• Title/Summary/Keyword: Wake characteristics

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Wind loads and load-effects of large scale wind turbine tower with different halt positions of blade

  • Ke, Shitang;Yu, Wei;Wang, Tongguang;Zhao, Lin;Ge, Yaojun
    • Wind and Structures
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    • v.23 no.6
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    • pp.559-575
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    • 2016
  • In order to investigate the influence of different blade positions on aerodynamic load and wind loads and load-effects of large scale wind turbine tower under the halt state, we take a certain 3 MW large scale horizontal axis three-blade wind turbine as the example for analysis. First of all, numerical simulation was conducted for wind turbine flow field and aerodynamic characteristics under different halt states (8 calculating conditions in total) based on LES (large eddy simulation) method. The influence of different halt states on the average and fluctuating wind pressure coefficients of turbine tower surface, total lift force and resistance coefficient, circular flow and wake flow characteristics was compared and analysed. Then on this basis, the time-domain analysis of wind loads and load-effects was performed for the wind turbine tower structure under different halt states by making use of the finite element method. The main conclusions of this paper are as follows: The halt positions of wind blade could have a big impact on tower circular flow and aerodynamic distribution, in which Condition 5 is the most unfavourable while Condition 1 is the most beneficial condition. The wind loads and load-effects of disturbed region of tower is obviously affected by different halt positions of wind blades, especially the large fluctuating displacement mean square deviation at both windward and leeward sides, among which the maximum response occurs in $350^{\circ}$ to the tower top under Condition 8; the maximum bending moment of tower bottom occurs in $330^{\circ}$ under Condition 2. The extreme displacement of blade top all exceeds 2.5 m under Condition 5, and the maximum value of windward displacement response for the tip of Blade 3 under Condition 8 could reach 3.35 m. All these results indicate that the influence of halt positions of different blades should be taken into consideration carefully when making wind-resistance design for large scale wind turbine tower.

Characteristics of accretion and scour around artificial reefs in the southern waters of Korea (한국 남해안에 시설된 인공어초 주위의 퇴적과 세굴 특성)

  • Kim, Chang-Gil;Suh, Sung-Ho;Oh, Tae-Gun;Kim, Byung-Gyun;Choi, Yong-Suk;Sheehy, Daniel J.
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2011.06a
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    • pp.233-233
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    • 2011
  • This study describes the characteristics of accretion and scour around artificial reefs in Korea. The survey for accretion and scour was made at a dice reef set consisting of 137 dice reefs. The volume of a dice reef unit is 8 $m^3$. The reef set was placed on the muddy sand at 21.6 m in November of 1999. Equipment used in the survey includes Side Scan Sonar, Multi Beam Echo Sounder, Sub-Bottom Profiler and water current meter. According to the results, the artificial reefs are heaped up at two to three times (4 m) the height of the dice reef. The maximum current around the artificial reefs was 81.5 cm/sec at the ebb tide and 72.7 cm/sec at the flood tide. Scour around artificial reefs occurs upstream to the flow while accretion is formed at wake zone in the downstream. The height of accretion ranges from 2.4 to 3.0 m. The crest of the accretion is formed at the distance of about 10 m from the edge of the reef. The slope of accretion is formed steeply at the vicinity of the reef which is at right angles to the direction of main current, and grows gently lower with the increased distance from the reef. Scour is continuously caused by upwelling from the reef set and by side currents that flow parallel to side of the accretion. Also, scour takes place on the deposited sediment rather than on the remaining bottom sediments. This means that, once fully formed, the depth of scour gully on both sides to the direction of main current hardly changes.

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Current Status of Response to Digital Child Sexual Slavery and Comparative Analysis of Overseas Crime Prediction System Using Artificial Intelligence (디지털 아동 성착취 대응현황과 해외 인공지능 범죄 예측 시스템 비교분석)

  • Kim, Hyejin
    • Journal of Digital Convergence
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    • v.18 no.7
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    • pp.357-368
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    • 2020
  • This study identifies the aspects and characteristics of 'Digital Sexual Crimes' that changed rapidly in recent years. It has identified the so-called "Telegram sexual harassment and exploitation" incident on the front page. We also want to analyze this and draw up policy suggestions that can help prepare social measures. In the wake of the Telegram sexual exploitation scandal, The National Assembly is quickly proposing related bills. However, the reality is that even a clear concept and definition of "Digital sexual Crimes" have not been made yet. The effective support system for victims is also insufficient. Therefore, this paper examines the definition and concept of child sexual exploitation and harassment. We will look at the features, causes, and conditions. In addition, it will examine the current status of Digital Sexual Crimes distribution and deletion of domestic, foreign platforms. Major foreign countries, including the U. S. A. refer to cases in which big data and artificial intelligence technologies are actively used to protect victims and track perpetrators.

Comparison of Sleep Patterns and Autonomic Nervous System Activity among Three Shifts in Shiftworkers (교대근무자에서 각 교대근무간의 수면양상 및 자율신경계 활성도 비교)

  • Yoon, In-Young;Ha, Mi-Na;Park, Jung-Sun;Song, Byoung-Gun
    • Sleep Medicine and Psychophysiology
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    • v.7 no.2
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    • pp.96-101
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    • 2000
  • Objectives: Through comparing sleep variables and autonomic activities among three shifts in shift workers, the authors intended to clarify which shift is most tolerable and to identify the characteristics of their psychological and physical problems. This study is also expected to help shift workers to adapt themselves to their work more effectively. Methods: Fifty one shift workers took part in this study. They were working in a rapidly rotating system in which they worked for 3 days in one shift with one day off between each shift. Based on a sleep diary, sleep latency (SL), sleep period time (SPT), and number of wake after sleep onset (NWASO) were estimated and compared among the three shifts. In assessing sleepiness, Epworth sleepiness scale (ESS) and visual analogue scale (VAS) were used. To evaluate mood states among the three shifts, profile of mood states (POMS) was administered. Heart rate variability (HRV), and the level of adrenaline and noradrenaline were measured to assess autonomic activities. HRV included low frequency power (LF), high frequency power (HF), and LF/HF. Results: SPT was significantly lengthened during the evening shift and SL was shortened during the night shift. The workers showed a drop in alertness at wake-up during morning shift and a drop in alertness at work during night shift. During night shift the subjects complained of physical fatigue and cognitive decline. Comparison of HRV showed that parasympathetic activity was most prominent during the evening shift. Secretion of adrenaline and noradrenaline decreased during the evening shift, though statistically not significant. Conclusion: We found that the evening shift was most tolerable among the three shifts. It is recommended that morning light exposure be done during the morning shift and nocturnal light exposure during the night shift.

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Development of KD- Propeller Series using a New Blade Section (새로운 날개단면을 이용한 KD-프로펠러 씨리즈 개발)

  • J.T. Lee;M.C. Kim;J.W. Ahn;H.C. Kim
    • Journal of the Society of Naval Architects of Korea
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    • v.28 no.2
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    • pp.52-68
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    • 1991
  • A new propeller series is developed using the newly developed blade section(KH18 section) which behaves better cavitation characteristics and higher lift-drag ratio at wide range of angle-of-attack. The pitch and camber distributions are disigned in order to have the same radial and chordwise loading distribution with the selected circumferentially averaged wake input. Since the geometries of the series propeller, such as chord length, thickness, skew and rate distribations, are selected by regression of the recent full scale propeller geometric data, the performance prediction of a propeller at preliminary design stage can be mure realistic. Number of blades of the series propellers is 4 and the expanded blade area ratios are 0.3, 0.45, 0.6 and 0.75. Mean pitch ratios are selected as 0.5, 0.65, 0.8, 0.75 and 1.1 for each expanded area ratio. The new propeller series is composed of 20 propellers and is named as KD(KRISO-DAEWOO) propeller series. Propeller open water tests are performed at the experimental towing tank, and the cavitation observation tests and fluctuating pressure measurements are carried out at the cavitation tunnel of KRISO. $B_{P}-\delta$ curves, which can be used to select the optimum propeller diameter at the preliminary design stage, are derived from a regression analysis of the propeller often water test results. The KD-cavitation chart is derived from the cavitation observation test results by choosing the local maximum lift coefficient and the local cavitation number as parameters. The caviy extent of a propeller can be predicted more accurately by using the KD-cavitation chart at a preliminary design stage, since it is derived from the results of the cavitation observation tests in the selected ship's wake, whereas the existing cavitation charts, such as the Burrill's cavitation chart, are derived from the test results in uniform flow.

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Association of Sleep Perception With Objective and Subjective Sleep Variables in Insomnia Patients (불면증 환자의 수면인식과 객관적, 주관적 수면변수의 연관성에 대한 연구)

  • Yoon, Gahui;Oh, Seong Min;Seo, Min Cheol;Lee, Mi Hyun;Yoon, So Young;Lee, Yu Jin
    • Sleep Medicine and Psychophysiology
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    • v.28 no.2
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    • pp.70-77
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    • 2021
  • Objectives: Our study aims to investigate the clinical and polysomnographic variables associated with subjective sleep perception. Methods: Among the patients who underwent nocturnal polysomnography (PSG) at the Center for Sleep and Chronobiology of Seoul National University Hospital from May 2018 to July 2019, 109 diagnosed with insomnia disorder based on DSM-5 were recruited for the study, and their medical records were retrospectively analyzed. Self-report questionnaires about clinical characteristics including Pittsburgh sleep quality index (PSQI), Beck depression inventory (BDI), and Epworth sleepiness scale (ESS) were completed. Subjective sleep quality was measured using variables of subjective total sleep time (subjective TST), subjective sleep onset latency (subjective SOL), subjective number of awakenings, morning feeling after awakening, and sleep discrepancy (subjective TST-objective TST) the morning after PSG. Pearson and Spearman correlation analyses were used to determine the factors associated with subjective sleep perception. Results: In patients with insomnia, subjective TST was negatively correlated with Wake After Sleep Onset (WASO) (p = 0.001) and N1 sleep (p = 0.039) parameters on polysomnography. Also, it was negatively correlated with PSQI (p < 0.001) and BDI (p = 0.014) scores. Sleep discrepancy was negatively correlated with PSQI score (p = 0.018). Morning feeling was negatively correlated with PSQI (p = 0.019) and BDI (p < 0.001) scores. Conclusion: Our results demonstrated that subjective sleep perception is associated with PSG variables (WASO and N1 sleep) and with PSQI and BDI scores. In clinical practice, it is helpful to assess and manage insomnia patients in consideration of objective sleep variables, subjective sleep quality, and depressed mood, which can influence subjective sleep perception.

Development of a Family Pattern Appraisal to Guide a Rogerian Nursing Practice (Rogers 이론에 근거한 가족양상 사정지침개발)

  • 이광옥;한영란;김희정
    • Journal of Korean Academy of Nursing
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    • v.25 no.4
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    • pp.751-773
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    • 1995
  • We, clinical nurse specialists practising and guiding student practice in a Community health nursing clinic, wanted to develop a family pattern appraisal consistent with Rogers' conceptual system, the nursing model guiding our practice. We use Rogers' model because it is harmonious with the traditional Korean view of the one human, natural and cosmic world. The purpose of our research was to contribute to science - based nursing practice, not only, one helpful model, but also a model of how to use, in guiding practice, a conceptual system which reflects nurse practitioners' philosophy of nursing, is intellectually satisfying, and enriches meaning in daily nursing life. The research objectives were to review the literature on Rogers' model and analyse it according to Kim's five - level analytical framework, to explore Rogers' definition of family, to review appraisals based on Rogers' model, and to develop a family appraisal which is culturally appropriate for use in our community. This work including the use of the appraisal and its refinement with families in our practice which was done during 1994 and 1995, in Seoul, in the Capital of the Republic of Korea. At the highest level of analysis, Rogers conceptual system emphasizes acausality and multidimentional meaning ; the world view is characterized by process, movement and wholeness. The epistemology Is one of holism and the knowledge base includes all forms of experience, from sensory to mystical, objective, and subjective. At the metaparadigm level, nursing focuses on the unitary human being and the environment. At the level of nursing philosophy, the model identifies human being, nursing, nurse, and illness and health. At the paradigm level the model assumes the irriducibility of the human to parts, noncausality and continual change. Rogers' practice methodology consists of pattern manifestation appraisal and deliberative mutual patterning. Under-standing patterns and patterning of people is the key to helping them achieve their potential. At the theory level, the basic assumptions, key concepts, and homeodynamic principles were identified. Rogers states the family energy field is an undividable, four-dimensional negentropic energy field which is in a larger envircinmental field show-ing such characteristics as cannot be predicted by knowledge of individual family members. Based on the word of Rogers scholars, we chose Rogers' correlates of patterning to understand the family unit as a whole-frequency, rhythms, motion, time perception, sleeping-waking beyond waking, pragmatic -imaginative-visionary to develop the appraisal. We, also used some of Barrel's (1988) criteria including interpersonal network and professional health care access and use, and Cordon's (1982) criteria including self perception - self concept modified to fit the family. Our family Pattern appraisal included 1. Influencirg data, 2. Professional health care access and use, 3. Family self perception-self concept, 4. Family interpersonal network, 5. Sleep-wake-be-yond waking, 6. Pragmatic-imaginary-visionary, 7. Family frequency and rhythm, 8. Family motion, 9. Family time perception. The appraisal was used with four families and modified to eliminate overlap and to make it possible for the family member to express themselves more easily. We plan to gain more experience with the appraisal toward further development of the tool.

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Experimental Study on the Fire Behavior in Double Deck Tunnel (복층터널내 화재특성에 대한 실험적 연구)

  • Park, Jin-Ouk;Yoo, Yong-Ho;Kim, Hwi-Seung;Park, Byoung-Jik
    • Fire Science and Engineering
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    • v.30 no.2
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    • pp.75-80
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    • 2016
  • In the wake of expanding and overpopulating urban areas, traffic congestion has been worsening increasingly, causing huge economic losses. In a bid to effectively use the space of metropolitan areas, the construction and operation of a double deck tunnel has been on the rise. On the other hand, a lower height of a double deck tunnel is expected to generate more smoke and soot in a fire than other usual tunnels. Therefore, it is undesirable to apply the standard for fire intensity or smoke generation, which were designed for existing road tunnels. A part of an effort to propose a design fire curve that is useful for double deck tunnel, is intended to obtain and analyze the fire characteristics in a double deck tunnel through a real scale fire test. The test was conducted according to the fire scenario with one passenger car and two passenger cars; the monitored fire intensity was a maximum of 2.4 MW and 3.5 MW, respectively.

Dynamic Response Analysis for Upper Structure of 5MW Offshore Wind Turbine System based on Multi-Body Dynamics Simulation (다물체 동역학 시뮬레이션 기반 5MW급 해상풍력발전시스템의 상부구조물에 대한 동적 응답 해석)

  • Lee, Kangsu;Im, Jongsoon;Lee, Jangyong;Song, Chang Yong
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.16 no.4
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    • pp.239-247
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    • 2013
  • Recently renewable energy such as offshore wind energy takes a higher interest due to the depletion of fossil fuel and the environmental pollution. This paper deals with multi-body dynamics (MBD) analysis technique for offshore wind turbine system considering aerodynamic loads and Thevenin equation used for determination of electric generator torque. Dynamic responses of 5MW offshore wind turbine system are evaluated via the MBD analysis, and the system is the horizontal axis wind turbine (HAWT) which generates electricity from the three blades horizontally installed at upwind direction. The aerodynamic loads acting on the blades are computed by AeroDyn code, which is capable of accommodating a generalized dynamic wake using blade element momentum (BEM) theory. In order that the characteristics of dynamic loads and torques on the main joint parts of offshore wind turbine system are simulated similarly such an actual system, flexible body modeling including the actual structural properties are applied for both blade and tower in the multi-body dynamics model.

Brain Based Teaching-learning Model Design about Life Drawing - Focusing on Animation Major Drawing (라이프 드로잉(life Drawing)의 두뇌 기반 교수-학습 전략 연구 - 애니메이션 전공 중심으로)

  • Park, Sung-Won
    • Cartoon and Animation Studies
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    • s.38
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    • pp.71-91
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    • 2015
  • This study is a process to study the life drawing teaching method considering professional characteristics in animation and has a study objective to design the model and teaching method which applies the strategies considering the creative mechanism of the brain. Recently, study results about integrated teaching method are being announced which apply brain based learning principles as the alternative arguments about teaching methods in each area based on creativeness. In other words, integrated education based on creative mechanism in the brain is applied not only to fine arts and drawing education, but also to the entire areas of the arts. Life drawing is an area which demands comprehensive teaching method that vivid expressions could be skillfully obtained by understanding the communication methods with the objects through cognitive senses, creativeness and movements beyond the structural knowledge about human body. Therefore in this study, the strategies and methods for the skillfulness of life drawing and consequently arranged education model structure drawing are to be designed based on the creativeness, study materials and content factors which were analyzed in previous stages of this study. In order to combine the content factors based on creativeness and study materials of the brain which are the results of previous studies, the conclusion has been reached that 5 step cognitive strategy stages to wake brain senses, flexibilize the brain, purify the brain, integrate the brain and become the master of the brain. Strategic methods to execute this were designed with brain gym, right brain energization drawing and HSP(high-level cognizance) training. Teaching and learning model structure diagram which is designed based on this is to be continued to teaching and learning guidelines during the relevant semesters after the research.