• Title/Summary/Keyword: low point

Search Result 5,350, Processing Time 0.034 seconds

Rapid Manufacturing of Microscale Thin-walled Structures using a Phase Change Work-holding Method

  • Shin Bo-Sung;Yang Dong-Yol
    • International Journal of Precision Engineering and Manufacturing
    • /
    • v.7 no.3
    • /
    • pp.47-50
    • /
    • 2006
  • High-speed machining is a very useful tool and one of the most effective rapid manufacturing processes. This study sought to produce various high-speed machining materials with excellent quality and dimensional accuracy. However, high-speed machining is not suitable for microscale thin-walled structures because the structure stiffness lacks the ability to resist the cutting force. This paper proposes a new method that is able to rapidly produce very thin-walled structures. This method consists of high-speed machining followed by filling. A strong work-holding force results from the solidification of the filling materials. Low-melting point metal alloys are used to minimize the thermal effects during phase changes and to hold the arbitrarily shaped thin-walled structures quickly during the high-speed machining. We demonstrate some applications, such as thin-walled cylinders and hemispherical shells, to verify the usefulness of this method and compare the analyzed dimensional accuracy of typical parts of the structures.

PROSPECTS IN DETERMINISTIC THREE-DIMENSIONAL WHOLE-CORE TRANSPORT CALCULATIONS

  • Sanchez, Richard
    • Nuclear Engineering and Technology
    • /
    • v.44 no.2
    • /
    • pp.113-150
    • /
    • 2012
  • The point we made in this paper is that, although detailed and precise three-dimensional (3D) whole-core transport calculations may be obtained in the future with massively parallel computers, they would have an application to only some of the problems of the nuclear industry, more precisely those regarding multiphysics or for methodology validation or nuclear safety calculations. On the other hand, typical design reactor cycle calculations comprising many one-point core calculations can have very strict constraints in computing time and will not directly benefit from the advances in computations in large scale computers. Consequently, in this paper we review some of the deterministic 3D transport methods which in the very near future may have potential for industrial applications and, even with low-order approximations such as a low resolution in energy, might represent an advantage as compared with present industrial methodology, for which one of the main approximations is due to power reconstruction. These methods comprise the response-matrix method and methods based on the two-dimensional (2D) method of characteristics, such as the fusion method.

Decision making for CDMA HPA Bias used Fuzzy Logic Controller (퍼지제어기를 이용한 CDMA중계기의 최적동작점 결정)

  • 김성식;홍광진;조현찬;오창헌;김두용;이규영
    • Proceedings of the Korean Institute of Intelligent Systems Conference
    • /
    • 2003.05a
    • /
    • pp.283-286
    • /
    • 2003
  • Generally, the repeater in CDMA(Code Division Multiple Access) included HPA(HI-Power Amplifier) to amplifier communication signals. Also, HPA contained PD(Predistortor) to maintain the linearization of amplifier characteristics A configuration component of PD have been used electricity nonlinear devices such that diode. But this diode takes many influences at the circumstance temperature. Consequently, st can't maintain output linearization, and drop the communication Duality. The manufacturer set bias of the circuit to the manual at the first out of ware-house low. But the Q-point changes according to the change of the high temperature or low temperature. Therefore, we designed a system to maintain the Q-point by FDM(Fuzzy Decision Maker) in this paper.

  • PDF

The Effect of Dynamic Strain Aging on the High Temperature Plastic Deformation Behaviour of Al-Mg Alloy (Al-Mg 합금의 고온 소성 변형 특성에 미치는 동적 변형 시효의 영향)

  • 이상용;이정환
    • Transactions of Materials Processing
    • /
    • v.5 no.4
    • /
    • pp.327-336
    • /
    • 1996
  • The effect of dynamic strain aging on high temperature deformation behaviour of the A-Mg alloy was investigated by strain rate change tests and stress relaxation tests between 20$0^{\circ}C$and 50$0^{\circ}C$. Yield point, short stress transient and periodic discontinuities on the stress-strain curve were considered as an evidence of the effect of dynamic strain aging. With this criterion two distinct strain rate-temperature regimes could be manifested. Dynamic strain aging was considered to be effective in the high temperature-low strain rate regime, whereas dynamic recovery was a dominant deformation mechanism in the low temperature-high strain rate regime. It was found that dynamic strain aging in the high temperature deformation was governed by the mechcanism of diffusion-controlled, viscous dislocation movement.

  • PDF

Flow Visualization of an Unsteady Airfoil at Low Reynolds Numbers (저 레이놀즈수에서 비정상 에어포일의 흐름 가시화)

  • Kim, Dong-Ha;Chang, Jo-Won
    • Journal of the Korean Society of Visualization
    • /
    • v.4 no.2
    • /
    • pp.51-58
    • /
    • 2006
  • A boundary layer visualization was carried out in order to investigate the influence of Reynolds number on an oscillating airfoil. An NACA 0012 airfoil is sinusoidally pitched at the quarter chord point with oscillation amplitude of ${\pm}6^{\circ}$. A smoke-wire technique was employed to visualize the boundary layer and the near-wake. The freestream velocities are 1.98, 2.83 and 4.03m/s and corresponding chord Reynolds numbers are $2.3{\times}10^4,\;3.3{\times}10^4$, and $4.8{\times}10^4$, respectively. As the reduced frequency of K=0.1 is fixed, the corresponding frequency of an airfoil was adjusted in each case. The results reveal that the point at which the shear stress in an unsteady boundary layer separation disappears does not correspond with the position of the breakdown of the boundary layer, and that the breakdown of the boundary layer occurs further downstream.

  • PDF

Performance Enhancement of Low-Cost Land Navigation System for Location-Based Service

  • Cho, Seong-Yun;Choi, Wan-Sik
    • ETRI Journal
    • /
    • v.28 no.2
    • /
    • pp.131-144
    • /
    • 2006
  • This work demonstrates a dead-reckoning (DR) scheme for a low-cost land navigation system and a DR/GPS system design using the sigma point Kalman filter (SPKF). T hrough an observability analysis and some simulations, it is shown that the performances of a stand-alone DR system and DR/GPS system can be improved by employing the proposed DR scheme and SPKF. By using the designed DR scheme and filter, the stand-alone DR system does not have any undetectable errors occurring on the curve trajectory. And the DR/GPS system can provide a stable and seamless navigational solution even in the case where the initial heading estimation error is large, such as 160 degrees, or when the GPS signal is unavailable due to tunnels, buildings, and so on. Simulation results indicate a satisfactory performance of the proposed system.

  • PDF

Design of a Low Noise Amplifier for Wireless LAN (무선 근거리 통신망용 저잡음 증폭기의 설계)

  • 류지열;노석호;박세현
    • Journal of the Korea Institute of Information and Communication Engineering
    • /
    • v.8 no.6
    • /
    • pp.1158-1165
    • /
    • 2004
  • This paper describes the design of a two stage 1V power supply SiGe Low Noise Amplifier operating at 5.25㎓ for 802.lla wireless LAN application. The achieved performance includes a gain of 17㏈, noise figure of 2.7㏈, reflection coefficient of 15㏈, IIP3 of -5㏈m, and 1-㏈ compression point of -14㏈m. The total power consumption of the circuit was 7㎽ including 0.5㎽ for the bias circuit.

Analysis of Multi-branch Inventory Distribution System for an Item with Low Level of Demand and Lost Sale Allowed (다지점으로 구성된 재고시스템의 최적화 분석 : 저수요, 유실판매 모형)

  • 윤승철;최영섭
    • Journal of Korean Society of Industrial and Systems Engineering
    • /
    • v.25 no.3
    • /
    • pp.78-84
    • /
    • 2002
  • This research is basically deals with an inventory distribution system with several regional sides branches. Under the continuous review policy, each sales branch places an order to its supplier whenever on hand plus on order inventory falls on the order point, and the order quantity is received after elapsing a certain lead time. This research first shows the method how to apply the product with low lever of demand into the continuous review policy. For the application, we use an order level as the maximum level of inventory during an order cycle. Also we analyze the lost sales case as a customer behavior. Further we use variable demands and variable lead times for more realistic situation. Based on the above circumstances, the research mainly discusses those methods to decide the optimal order level, order point, and order quantity for each sales branch which guarantees the system wide goal level of service, while keeping the minimum level of the system wide total inventory.

A Design of Power Circuit and LCL Filter for Switching Mode PV Simulator (스위칭방식 PV Simulator의 전력회로와 LCL필터 설계)

  • Lee, Sung-Min;Yu, Tae-Sik;Kim, Hyo-Sung
    • The Transactions of the Korean Institute of Power Electronics
    • /
    • v.17 no.5
    • /
    • pp.431-437
    • /
    • 2012
  • PV simulators are essential equipment for testing power conditioning systems (PCS) which are one of an important part in PV generator systems, for testing before shipment. High dynamic PV simulator is required since MPPT(Maximum Power Point Tracking) test procedure has been established by EN50530 regulation recently. Most high quality PV simulator prevailed in the market is linear type which however has low efficiency. This paper proposes design guide lines for the power stage and LCL type filter cooperating with a switching mode PV simulator that shows high efficiency and very low power consumption. Proposed theory is verified by experiment.

A Study on High Temperature Low Cycle Fatigue Crack Growth Modelling by Neural Networks (신경회로망을 이용한 고온 저사이클 피로균열성장 모델링에 관한 연구)

  • Ju, Won-Sik;Jo, Seok-Su
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.20 no.4
    • /
    • pp.2752-2759
    • /
    • 1996
  • This paper presents crack growth analysis approach on the basis of neural networks, a branch of cognitive science to high temperature low cycle fatigue that shows strong nonlinearity in material behavior. As the number of data patterns on crack growth increase, pattern classification occurs well and two point representation scheme with gradient of crack growth curve simulates crack growth rate better than one point representation scheme. Optimal number of learning data exists and excessive number of learning data increases estimated mean error with remarkable learning time J-da/dt relation predicted by neural networks shows that test condition with unlearned data is simulated well within estimated mean error(5%).