• 제목/요약/키워드: Micro spring

검색결과 149건 처리시간 0.026초

Climatological Variability of Satellite-derived Sea Surface Temperature and Chlorophyll in the South Sea of Korea and East China Sea (남해와 동중국해에서 위성으로 추정된 표층수온 및 클로로필의 장기 변화)

  • Son, Young-Baek;Ryu, Joo-Hyung;Noh, Jae-Hoon;Ju, Se-Jong;Kim, Sang-Hyun
    • Ocean and Polar Research
    • /
    • 제34권2호
    • /
    • pp.201-218
    • /
    • 2012
  • The purpose of this study is to investigate climatological variations from the sea surface temperature (SST), chlorophyll-a concentration (Chl-a), and phytoplankton size class (PSC), using NOAA AVHRR, SeaWiFS, and MODIS data in the South Sea of Korea (SSK) and East China Sea (ECS). 26-year monthly SST and 13-year monthly Chl-a and PSC data, separated by whole and nine-different areas, were used to understand seasonal and inter-annual variations. SST and Chl-a clearly showed seasonal variations: higher SST and Chl-a were observed during the summer and spring, and lower values occurred during the winter and summer. The annual and monthly SST over 26 years increased by $0.2{\sim}1.0^{\circ}C$. The annual and monthly Chl-a concentration over 13 years decreased by $0.2{\sim}1.1mg/m^3$. To determine more detailed spatial and temporal variations, we used the combined data with monthly SST, Chl-a, and PSC. Between 1998 and 2010, the inter-annual trend of Chl-a decreased, with decreasing micro- and nano-size plankton, and increasing pico-size plankton. In regional analysis, the west region of the study area was spatially and temporally correlated with the area dominated by decreasing micro-size plankton; while the east region was less sensitive to coastal and land effects, and was dominated by increasing pico-size plankton. This phenomenon is better related to one or more forcing factors: the increased stratification of ocean driven by changes occurring in spatial variations of the SST caused limited contributions of nutrients and changed marine ecosystems in the study area.

A Fourier sine series solution of static and dynamic response of nano/micro-scaled FG rod under torsional effect

  • Civalek, Omer;Uzun, Busra;Yayli, M. Ozgur
    • Advances in nano research
    • /
    • 제12권5호
    • /
    • pp.467-482
    • /
    • 2022
  • In the current work, static and free torsional vibration of functionally graded (FG) nanorods are investigated using Fourier sine series. The boundary conditions are described by the two elastic torsional springs at the ends. The distribution of functionally graded material is considered using a power-law rule. The systems of equations of the mechanical response of nanorods subjected to deformable boundary conditions are achieved by using the modified couple stress theory (MCST) and taking the effects of torsional springs into account. The idea of the study is to construct an eigen value problem involving the torsional spring parameters with small scale parameter and functionally graded index. This article investigates the size dependent free torsional vibration based on the MCST of functionally graded nano/micro rods with deformable boundary conditions using a Fourier sine series solution for the first time. The eigen value problem is constructed using the Stokes' transform to deformable boundary conditions and also the convergence and accuracy of the present methodology are discussed in various numerical examples. The small size coefficient influence on the free torsional vibration characteristics is studied from the point of different parameters for both deformable and rigid boundary conditions. It shows that the torsional vibrational response of functionally graded nanorods are effected by geometry, small size effects, boundary conditions and material composition. Furthermore, for all deformable boundary conditions in the event of nano-sized FG nanorods, the incrementing of the small size parameters leads to increas the torsional frequencies.

The Microalgal Attachment and its Growth on the Artificial Surfaces Immersed in Seawater: I. Attachment and Micro-succession (해수에 잠긴 인공기질 표면에서 미세조류의 부착과 성장: I. 부착 및 천이)

  • Shim, Jae-Hyung;Kang, Jung-Hoon;Cho, Byung-Cheol;Kim, Woong-Seo
    • The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
    • /
    • 제3권4호
    • /
    • pp.249-260
    • /
    • 1998
  • To understand the attachment of micro algae and their subsequent growths on artificial surfaces immersed in seawater, the relationship between attachment of diatoms on the immersed artificial substrates and species pool in the surrounding water was investigated. We used acryl slides for the study of diatom attachment and examined the surrounding water samples collected in Incheon Harbour from July 1995 to February 1997. Variations of species composition and abundances by exposure time in seawater were investigated during the early phase of biofilm formation on various substrates, e.g. glass, acryl, titanium, copper and antifouling paint-treated slides. Immigration rates of diatoms to acryl slides during spring and winter were significantly correlated with the abundance of benthic diatoms in surrounding water ($r^2$=0.78, p<0.01, n=42), suggesting that immigration rates were affected by variations of benthic diatom abundances in surrounding water. Immigration coefficient of monoraphid diatoms was 5 times higher than that of biraphid diatoms, but relative abundance of monoraphid diatoms was 3 times lower than that of biraphid diatoms on acryl slides in spring. In winter, immigration coefficient and relative abundance of centric diatoms were higher compared to other raphe forms. These results suggest that the attachment of diatoms seems to be caused by the abundance and immigration coefficients of benthic diatoms in surrounding water. Pennate diatoms predominantly attached to all artificial surfaces throughout all experimental periods. Interestingly, centric diatoms predominantly attached to all artificial surfaces in winter. Hantzschia virgata, Licmophora abbreviata and Melosira nummuloides appeared dominantly on antifouling paint-treated slides, probably being tolerant of the antifouling paint. During incubations, the abundance of attached diatoms increased exponentially on glass, titanium and acryl slides with exposure time. The maximum abundance was highest on glass slide, followed by acryl, titanium, copper and antifouling paint-treated slides. The growth rates of attached diatom community on all artificial surfaces were higher at temperature of $24-25^{\circ}C$ than that of $2-3^{\circ}C$. The growth rate of attached diatoms on glass slide was generally higher compared to other slides during the study period. Dominant morphotypes of observed species with exposure time in seawater were prostrate form Amphora coffeaeformis, fan shape Synedra tabulata, stalk type Licmophora paradoxa and chain type M. nummuloides. A micro-succession in the attached microalgal community was observed. The composition of dominant species seems to be the result of species-specific response to gradually limited space with development of microalgal film.

  • PDF

Changes of Soil Temperature and Moisture under the Agrivoltaic Systems in Fallow Paddy Field during Spring Season (봄철 영농형 태양광 시설 하부 휴경논 토양의 온도와 수분 변화)

  • Yuna Cho;Euni Cho;Jae-Hyeok Jeong;Hoejeong Jeong;Woon-Ha Hwang;Jaeil Cho
    • Korean Journal of Agricultural and Forest Meteorology
    • /
    • 제25권3호
    • /
    • pp.218-225
    • /
    • 2023
  • An agrivoltaic system (AVS) is a combined system that generates power through photovoltaic panels (PVPs) installed above a field where a crop is cultivated. Although soil moisture is an important limiting factor for open-field crop production, particularly during spring season in Korea, it is not well considered in the utilization of AVS. Indeed, the application of water-energy-food nexus on the AVS should be necessary. In this study, the changes of soil moisture and temperature under the AVS was investigated in fallow paddy field during spring season. The AVS that has partial shading condition by PV panels was decreased soil temperature and increased soil moisture compared to open-field. Furthermore, the maximum of the change in soil moisture to the change in soil temperature had a negative correlation both on open-field and AVS under wet condition. It represents that the micro-climate under the AVS is in energy-limited condition. The open-field of relatively high soil temperature was in water-limited condition. The different behavior of soil moisture on the AVS should be considered for the sustainable agricultural system as related to water-energy-food nexus.

High-Performance Multimodal Flexible Tactile Sensor Capable of Measuring Pressure and Temperature Simultaneously (압력과 온도측정 기능을 갖는 고성능 플렉시블 촉각센서)

  • Jang, Jin-Seok;Kang, Tae-Hyung;Song, Han-Wook;Park, Yon-Kyu;Kim, Min-Seok
    • Journal of the Korean Society for Precision Engineering
    • /
    • 제31권8호
    • /
    • pp.683-688
    • /
    • 2014
  • This paper presents a high-performance flexible tactile sensor based on inorganic silicon flexible electronics. We created 100 nm-thick semiconducting silicon ribbons equally distributed with 1 mm spacing and $8{\times}8$ arrays to sense the pressure distribution with high-sensitivity and repeatability. The organic silicon rubber substrate was used as a spring material to achieve both of mechanical flexibility and robustness. A thin copper layer was deposited and patterned on top of the pressure sensing layer to create a flexible temperature sensing layer. The fabricated tactile sensor was tested through a series of experiments. The results showed that the tactile sensor is capable of measuring pressure and temperature simultaneously and independently with high precision.

Nonlinear large deformation dynamic analysis of electroactive polymer actuators

  • Moghadam, Amir Ali Amiri;Kouzani, Abbas;Zamani, Reza;Magniez, Kevin;Kaynak, Akif
    • Smart Structures and Systems
    • /
    • 제15권6호
    • /
    • pp.1601-1623
    • /
    • 2015
  • Electroactive polymers have attracted considerable attention in recent years due to their sensing and actuating properties which make them a material of choice for a wide range of applications including sensors, biomimetic robots, and biomedical micro devices. This paper presents an effective modeling strategy for nonlinear large deformation (small strains and moderate rotations) dynamic analysis of polymer actuators. Considering that the complicated electro-chemo-mechanical dynamics of these actuators is a drawback for their application in functional devices, establishing a mathematical model which can effectively predict the actuator's dynamic behavior can be of paramount importance. To effectively predict the actuator's dynamic behavior, a comprehensive mathematical model is proposed correlating the input voltage and the output bending displacement of polymer actuators. The proposed model, which is based on the rigid finite element (RFE) method, consists of two parts, namely electrical and mechanical models. The former is comprised of a ladder network of discrete resistive-capacitive components similar to the network used to model transmission lines, while the latter describes the actuator as a system of rigid links connected by spring-damping elements (sdes). Both electrical and mechanical components are validated through experimental results.

Development of Mobile Robot for Rough Terrain (야지 주행을 위한 견마형 로봇 개발)

  • Lee, Ji-Hong;Shim, Hyung-Won;Jo, Kyoung-Hwan;Hong, Ji-Mi;Kim, Jung-Bae;Kim, Sung-Hun
    • Journal of Institute of Control, Robotics and Systems
    • /
    • 제13권9호
    • /
    • pp.883-895
    • /
    • 2007
  • In this work, we present the development of a patrol robot which is intended to navigate outdoor rough terrain. Proposed mechanism consists of six legs for overcoming an obstacle, and six wheels for traveling. Also, in order to absorb vibration in rough terrain effectively, the slide-spring system and tubed type tire are adopted to each leg and each wheel. The control system of robot consists of several imbedded boards for management of lots of diverse devices such as sensors designed for rough terrain, motor controllers, camera, micro controller and so on. And the base system of the robot is designed to operate in real time and to surveille in the vicinity of the robot, and the robot system is controlled by wireless LAN connected to GUI-based remote control system, while CAN communication connects the control board and the device controllers for sensors and motor controllers. For operating this robot system efficiently, we propose the control algorithms for autonomous navigation using GPS, stabilization maintenance by posture control, obstacle-avoidance by impedance control, and obstacle-overcoming with interference-avoidance between wheels. The performance of the robot and the proposed algorithms are tested and proved by a set of experiments in outdoor rough terrain.

Studies on MEMS Inertial Switch Applicable to the Ignition SAU(Safe-Arm-Unit) of Propulsion System (추진기관 점화안전장치에 적용 가능한 MEMS 관성 스위치 연구)

  • Jang, Seung-Gyo;Jung, Hyung-Gyun
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 한국추진공학회 2010년도 제35회 추계학술대회논문집
    • /
    • pp.126-129
    • /
    • 2010
  • MEMS(micro electro-mechanical systems) inertial switch which is applicable to the ignition Safe-Arm- Unit of propulsion system is devised. The MEMS inertial switch is designed according to the general design procedure for conventional mechanical elements. Unlikely conventional MEMS accelerometer, threshold inertial switching mechanism is adopted which makes a MEMS element an abrupt switching in a certain acceleration level. By comparing the design data and test results of the specimen a small discrepancy in switching acceleration level is found which is presumably due to the nonlinear characteristics of the beam spring and the flexure hinge which are the main parts of the MEMS inertial switch.

  • PDF

Reliability analysis-based conjugate map of beams reinforced by ZnO nanoparticles using sinusoidal shear deformation theory

  • Keshtegar, Behrooz;Kolahchi, Reza
    • Steel and Composite Structures
    • /
    • 제28권2호
    • /
    • pp.195-207
    • /
    • 2018
  • First-order reliability method (FORM) is enhanced based on the search direction using relaxed conjugate reliability (RCR) approach for the embedded nanocomposite beam under buckling failure mode. The RCR method is formulated using discrete conjugate map with a limited scalar factor. A dynamical relaxed factor is proposed to control instability of proposed RCR, which is adjusted using sufficient descent condition. The characteristic of equivalent materials for nanocomposite beam are obtained by micro-electro-mechanical model. The probabilistic model of nanocomposite beam is simulated using the sinusoidal shear deformation theory (SSDT). The beam is subjected to external applied voltage in thickness direction and the surrounding elastic medium is modeled by Pasternak foundation. The governing equations are derived in terms of energy method and Hamilton's principal. Using exact solution, the implicit buckling limit state function of nanocomposite beam is proposed, which is involved various random variables including thickness of beam, length of beam, spring constant of foundation, shear constant of foundation, applied voltage, and volume fraction of ZnO nanoparticles in polymer. The robustness, accuracy and efficiency of proposed RCR method are evaluated for this engineering structural reliability problem. The results demonstrate that proposed RCR method is more accurate and robust than the excising reliability methods-based FORM. The volume fraction of ZnO nanoparticles and the applied voltage are the sensitive variables on the reliable levels of the nanocomposite beams.

Study on the Evaluation and Prediction of Micro-Defects in the Hemming Process (헤밍 공정에서의 미세 결함 평가 및 예측에 관한 연구)

  • Jung H. C.;Lim J. K.;Kim H. J.
    • Transactions of Materials Processing
    • /
    • 제14권6호
    • /
    • pp.533-540
    • /
    • 2005
  • The hemming process, composed of flanging, pre-hemming and main hemming, is the last one of a series of forming processes conducted on the automotive panels, having greater influence on the outward appearance of cars rather than on their performance. The hem quality can be quantitatively defined by the hemming defects including turn-down/up, warp and roll-in/out. However, it is difficult to evaluate and predict the hem quality through an experimental measurement or a numerical calculation since the size of defects is very small. This study aims to precisely evaluate the hemming defects, especially turn-down and roll-in, through numerical and experimental approaches and to investigate the influence of process parameters on the hem quality, focused on how to simulate the same conditions as in the experiment by the finite element analysis (FEA). The FEA results on the turn-down and roll-in obtained from a model composed of the optimum-sized elements, including a spring element linked to the flanging pad, and given the double master contact condition between the inner and outer panels, had a good correlation with the experimental data. It is thought possible to make an early estimate of the hem quality in a practical automotive design by applying the methodology proposed in this study.