• Title/Summary/Keyword: Dynamic focusing

Search Result 390, Processing Time 0.025 seconds

Numerical Study on the Shock Wave Focusing of Elliptic Reflectors (타원형 반사면에 의한 충격파 초점 변화에 관한 수치적 연구)

  • Ko C. C.;Shim E. B.;Sah J. Y.
    • Journal of computational fluids engineering
    • /
    • v.4 no.3
    • /
    • pp.35-43
    • /
    • 1999
  • In this study, the shock wave focusing of an elliptic reflector is numerically simulated by solving the Euler equations. The numerical method is the second order upwind TVD scheme with a finite volume discretization. For the verification of the present method, we simulate the moving shock wave passing through a two-dimensional corner. The computed isopycnics are compared with the earlier experiment. Numerical results of the elliptic reflectors show that the density and pressure at the focusing point increase linearly as the aspect ratio of the reflector becomes deep. On the other hand, the gas dynamic focal length decreased with the increase of the reflector aspect ratio.

  • PDF

Development of A Small VCM Focusing Actuator (초소형 VCM 포커싱 액츄에이터 개발)

  • Shin, Young-Chul;Lee, Seung-Yop;Park, Young-Phil
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • 2005.11a
    • /
    • pp.750-755
    • /
    • 2005
  • This paper proposes a small VCM (Voice coil motor) type actuator using curved suspensions for auto-focusing and zoom motions for mobile information devices. 1'he proposed focusing actuator adopts a nontraditional type of suspension using curved beams in order to extend output displacement within small height restriction. The curved beam is similar to the leaf spring type which is usually used in optical disk drives. In addition, three different materials are considered for the curved suspension model, and Aluminum shows the best dynamic characteristics. The proposed zoom actuator does not use a suspension supporting bobbin but a moving rail and a sloper mechanism by generating rotational force at lens holder. The sensitivity of design parameters on output performance is studied using ANSYS (3D FEM tool). Experiments using a prototype of the proposed actuator model verified the analytical prediction and performance.

  • PDF

Model for the Inertial Focusing of Particles Using an Atmospheric Aerodynamic Lens (상압 공기역학적 렌즈의 입자 관성집속 모델)

  • Lee, Jin-Won;Lee, Min-Yeong
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.25 no.3
    • /
    • pp.315-321
    • /
    • 2001
  • Aerodynamic lenses are widely used in generating particle beams of high density and small diameter, but analytical or modeling studies are limited only in the free molecular regime. In this study, it is shown that generating particle beam is also possible in atmospheric pressure range, and the mechanism of generating particle beam using an orifice is analysed into three different parts : fluid dynamic contraction, diffusional defocusing, and inertial focusing. In laminar flow conditions, the diffusional defocusing effect can be neglected, and the effects of inertial focusing can be expressed in terms of the orifice size and Stokes number. Numerical experiments are done for two different orifices, d/D=1/5 and 1/10 and particle diameter d(sub)p=1-10 ㎛. The results for two different orifices can be made into a single curve when a modified Stokes number is used. The inertial focusing effect diminishes when the modified Stokes number becomes smaller than 10(sup)-2.

Dynamic Response of Blade Surface Cavitation

  • Toyoshima, Masakazu;Sakaguchi, Kimiya;Tsubouchi, Kota;Horiguchi, Hironori;Sugiyama, Kazuyasu
    • International Journal of Fluid Machinery and Systems
    • /
    • v.9 no.2
    • /
    • pp.160-168
    • /
    • 2016
  • In high speed turbopumps, cavitation occurs and often causes the flow instabilities such as cavitation surge and rotating cavitation. The occurrence of these cavitation instabilities is considered to relate to dynamic characteristics of the cavitation, which are modelled using a cavitation compliance and a mass flow gain factor. Various types of cavitation such as a blade surface cavitation, a tip leakage vortex cavitation, and a backflow vortex cavitation occur at the same time in the inducer and the dynamic characteristics of each cavitation have not been clarified yet in experiments. Focusing on the blade surface cavitation as one of fundamental cavitation, we investigated the dynamic characteristics of the blade surface cavitation on a flat plate hydrofoil in experiments in the present study.

High School Student-Teachers Attempts to Justify Mathematical Propositions Utilizing Spatial Structuring on Shape Transform

  • Rahim, Medhat H.;Siddo, Radcliffe A.
    • Research in Mathematical Education
    • /
    • v.16 no.2
    • /
    • pp.107-123
    • /
    • 2012
  • A group of twenty-nine high school student-teachers were given a set of mathematical propositions focusing on shape-to-shape transformations. Their task was to determine through hands-on manipulation and use of dynamic software that each shape be transformed into an area equivalent rectangular region. This paper reports on a classroom-based research.

An Experimental Analysis on the Pier Dynamic Property Change with Penetration Depths (근입깊이에 따른 콘크리트 교각의 동특성 변화에 관한 실험적 연구)

  • Park, Byung-Cheol;Park, Seung-Bum
    • Proceedings of the Korea Concrete Institute Conference
    • /
    • 2004.11a
    • /
    • pp.655-658
    • /
    • 2004
  • This study was performed to verify the possibility of the integrity estimation of the bridge substructure focusing on the dynamic property change of concrete pier with penetration depths using experimental modal analysis. As a result of the impact vibration test, it is found that scour reduces the stiffness of the foundation, and measurement the accelerance residue and natural frequency can be used for the estimation of the integrity index.

  • PDF

Development of A Small VCM Focusing Actuator Using Curved Suspensions (곡선 서스펜션을 사용한 초소형 VCM 포커싱 구동기 개발)

  • Shin, Young-Chul;Lee, Seung-Yop
    • Transactions of the Korean Society for Noise and Vibration Engineering
    • /
    • v.18 no.1
    • /
    • pp.11-19
    • /
    • 2008
  • This paper proposes small VCM(voice coil motor) type, auto-focusing and zoom actuators for mobile information devices. In order to meet the large output displacement within small height restriction, the proposed auto-focusing actuator adopts curved suspensions, which are similar to a leaf-spring type suspension of optical disk drives. The sensitivity of design parameters on output displacement and dynamic performance is implemented using ANSYS (3D FEM tool) to determine the optimal geometry and stiffness of the curved suspensions. This paper also investigates a new zoom actuator without a suspension supporting a bobbin. The zoom actuator uses a moving rail and a stoper mechanism by generating rotational force at lens holder. Magnetic flux density of the zoom actuator are calculated by both the FEM and permeance method. Experiments using prototypes of the proposed focusing and zoom models show that both actuators meet the required displacement and performance.

Knowledge-driven Dynamic Capability and Organizational Alignment: A Revelatory Historical Case

  • Kim, Gyeung-Min
    • Asia pacific journal of information systems
    • /
    • v.20 no.1
    • /
    • pp.33-56
    • /
    • 2010
  • The current business environment has been characterized as less munificent, highly uncertain and constantly evolving. In this environment, the company with dynamic capability is reported to be more successful than others in building competitive advantage. Dynamic capability focuses on the link between a dynamically changing environment, strategic agility, architectural reconfiguration, and value creation. Being characterized to be flexible and adaptive to market circumstance changes, an organization with dynamic capability is described to have high resource fluidity, which represents business process, resource allocation, human resource management and incentives that make business transformation faster and easier. Successful redeployment of the resources for dynamic adaptation requires organizational forms and reward systems to be well aligned with firm's technological infrastructures and business process. The alignment is considered to be an executive level commitment. Building dynamic capability is knowledge driven; relying on new knowledge to reconfigure firm's resources. Past studies established the link between the effective execution of a knowledge-focused strategy and relevant setting of architectural elements such as human resources, structure, process and information systems. They do not, however, describe in detail the underlying processes by which architectural elements are adjusted in coordinated manners to build knowledge-driven dynamic capability. In fact, understandings of these processes are one of the top issues in IT management. This study analyzed how a Korean corporation with a knowledge-focused strategy aligned its architectural elements to develop the dynamic capability and thus create value in the dynamically changing markets. When the Korean economy was in crisis, the company implemented a knowledge-focused strategy, restructured the organization's architecture by which human and knowledge resources are identified, structured, integrated and coordinated to identify and seize market opportunity. Specifically, the following architectural elements were reconfigured: human resource, decision rights, reward and evaluation systems, process, and IT infrastructure. As indicated by sales growth, the reconfiguration helped the company create value under an extremely turbulent environment. According to Ancona et al. (2001), depending on the types of lenses the organization uses, different types of architecture will emerge. For example, if an organization uses political lenses focusing on power, influence, and conflict. the architecture that leverage power and negotiate across multiple interest groups would emerge. Similarly, if an organization uses economic lenses focusing on the rational behavior of organizational actors making choices based on the costs and benefits of action, organizational architecture should be designed to motivate and provide incentives for the actors (Smith, 2001). Compared to this view, information processing perspectives consider architecture to be designed to maximize the capacity of information processing by the actors. Using knowledge lenses, the company studied in this research established architectural elements in a manner that allows the firm to effectively structure knowledge resources to form dynamic capability. This study is revelatory single case with a historic perspective. As a result of this study, a set of propositions and a framework are derived, which can be used for architectural alignment.

A Study on an Ultrasonic Phased Array Transducer with a Spherical Liquid Lens (구면 액체 렌즈 초음파 위상 배역 변환기에 관한 연구)

  • 윤영중;박한규
    • Journal of the Korean Institute of Telematics and Electronics A
    • /
    • v.32A no.11
    • /
    • pp.9-16
    • /
    • 1995
  • In this paper, an ultrasonic phased array transducer with spherical liquid lens, which utilizes both electronic focusing by linear phased array and variable geometric focusing by spherical lens. is investigated. This system reduces the elevational beamwidth which is disadvantage of the 1-dimensional linear phased array, and adds real-time dynamic focusing capability by controlling the volume of liquid in the lens. A prototype of this transducer is constructed and tested. The experimental results are compared with those of computer simulations. The range of applications are in the hyperthermia applicators or ultrasonic image system with narrow beam and rapid scanning characterisitcs.

  • PDF

A Study on the improvement a Resolution of the Ultrasound Imaging System (초음파 영상장치에서 해상도 향상에 관한 연구)

  • Lee, Hoo-Jeong;Kim, Young-Kil;Lee, Haing-Sei
    • Proceedings of the KIEE Conference
    • /
    • 1987.07b
    • /
    • pp.1235-1238
    • /
    • 1987
  • In this paper, a new focusing method, to be called the sampled delay focusing (SDF), is proposed. This method improves the lateral resolution in ultrasound imaging system. In SDF, the analog delay lines are no longer necessary because sampling sum process can replace the conventional delay sum process. Also, this method offers continuous dynamic focusing on the resolution pixel basis if the maximum delay time is less than the sampling interval. Second order sampling is adopted in order to extend the sampling interval.

  • PDF