• Title/Summary/Keyword: cross ratio

Search Result 2,697, Processing Time 0.031 seconds

Flow characteristics of a cross jet issued in the fully developed pipe flow (파이프유동장에 분사되는 제트의 유동특성 연구)

  • Kim, Gyeong-Cheon;Sin, Dae-Sik
    • Transactions of the Korean Society of Mechanical Engineers B
    • /
    • v.22 no.7
    • /
    • pp.927-936
    • /
    • 1998
  • In the fully developed pipe flow, when jet is injected in cross to the flow there are complex transition flows caused by interaction of the cross flow and jet. These interactions are studied by means of the flow visualization methods and frequency analysis using a hot-wire anemometer. The velocity range of cross flow of the pipe is 0.3 m/s ~ 1.2 m/s and the corresponding Reynolds number, R$\sub$p/, based on the pipe diameter is 2.25 * 10$\^$3/ ~ 9.02 * 10$\^$3/. The velocity ratio (R), jet velocity/cross flow velocity, is chosen from 2 to 10. A circular cylinder is placed in the pipe instead of jet to observe the vortex shedding from the solid body. To compare the jet and circular cylinder flow, the vortical structure is analyzed in both cases and the structure of vortices and the origin of its formation are investigated, especially. The vortex shedding of the dominant coherent structure is compared between the jet flow and the circular cylinder flow. In the case of the jet flow, the Strouhal numbers are different depending on the existence of the upright vortex as well as the velocity ratio (R).

Characteristics of Droplet Properties in the Two-Phase Spray into a Subsonic Cross Flow

  • Lee, I.C.;Cho, W.J.;Koo, J.Y.
    • Proceedings of the Korean Society of Propulsion Engineers Conference
    • /
    • 2008.03a
    • /
    • pp.358-363
    • /
    • 2008
  • The spray cross-section characteristics of two-phase spray that using external-mixing nozzle injected into a subsonic cross flow were experimentally studied with various ALR ratio that is $0{\sim}59.4%$. Suction type wind tunnel was used and experiments were conducted to ambient environment. Several plain orifice nozzles with L/d of 30 and orifice diameter of 0.5 mm and orifice length 1.5 mm were tested. Free stream velocity profiles at the injection location were measured using hot wire. Spray images were captured to study collision point and column trajectory. Phase Doppler particle analyzer(PDPA) was utilized to quantitatively measuring droplet SMD, volume flux. Measuring probe of PDPA positions was moved 3-way transverse machine. SMD distributions were layered structure and peaked at the top of the spray plume and low value at bottom of the spray. Volume flux of spray was distributed to the two side region and volume flux quantity decreased when ALR ratio increased. It was found that the perpendicularly injected two-phase spray jet of external mixing into a cross flow showing that mistlike spray moved away from the test section bottom region.

  • PDF

The Determinants of Future Bank Stock Returns in Eight Asian Countries

  • An, Jiyoun;Na, Sung-O
    • East Asian Economic Review
    • /
    • v.18 no.3
    • /
    • pp.253-276
    • /
    • 2014
  • We examine which traditional asset pricing variables together with bank-specific accounting variables explain the cross-sectional variation of future bank stock returns, using a firm-level data of eight Asian countries. Our empirical evidence shows that exchange rate risk, firm size, the book-to-market ratio, and the net income ratio are important in explaining future bank stock returns during normal times. However, during the Global Financial Crisis period, different variables such as local market beta, illiquidity risk, equity ratio, and off-balance sheets ratio were statistically significant. Thus, researchers and policy practitioners should monitor these variables during normal times as well as during times of crisis.

Robust Blind Source Separation to Noisy Environment For Speech Recognition in Car (차량용 음성인식을 위한 주변잡음에 강건한 브라인드 음원분리)

  • Kim, Hyun-Tae;Park, Jang-Sik
    • The Journal of the Korea Contents Association
    • /
    • v.6 no.12
    • /
    • pp.89-95
    • /
    • 2006
  • The performance of blind source separation(BSS) using independent component analysis (ICA) declines significantly in a reverberant environment. A post-processing method proposed in this paper was designed to remove the residual component precisely. The proposed method used modified NLMS(normalized least mean square) filter in frequency domain, to estimate cross-talk path that causes residual cross-talk components. Residual cross-talk components in one channel is correspond to direct components in another channel. Therefore, we can estimate cross-talk path using another channel input signals from adaptive filter. Step size is normalized by input signal power in conventional NLMS filter, but it is normalized by sum of input signal power and error signal power in modified NLMS filter. By using this method, we can prevent misadjustment of filter weights. The estimated residual cross-talk components are subtracted by non-stationary spectral subtraction. The computer simulation results using speech signals show that the proposed method improves the noise reduction ratio(NRR) by approximately 3dB on conventional FDICA.

  • PDF

Driving Characteristics of the Cross Type Ultrasonic Rotary Motor Dependent on Shape of the Stator (스테이터의 형태에 따른 Cross형 초음파 회전모터의 구동특성)

  • Chong, Hyon-Ho;Park, Tae-Gone
    • The Transactions of the Korean Institute of Electrical Engineers C
    • /
    • v.54 no.10
    • /
    • pp.433-437
    • /
    • 2005
  • This paper studied Rotary type ultrasonic motor which has cross type stator. The stator consists of hollowed cross type metal which has four piezoelectric ceramics on the ends of cross bars. When two harmonic voltages which have 90$^{\circ}$ phase difference given to ceramics, the elliptical motion was generated in the inside tips. Inside tips are contact with rotor and these elliptical motions are rotate the rotor The finite element analysis was used to optimize the dimension and displacement of the stator. And the analyzed results were compared with the experimental results of the motor. As results, the speed and the torque of motor was increased by increasing width of the cross bar. And the speed and torque o( motor was not influenced to length of cross bar. The speed and torque was linearly increased by increasing voltage. The maximum torque was generated when the motor fabricated length of cross bar and width of ceramics in the ratio of 1:2.

Empirical Correlations for Penetration Height of Liquid Jet in Uniform Cross Flow - A Review

  • No, Soo-Young
    • Journal of ILASS-Korea
    • /
    • v.16 no.4
    • /
    • pp.176-185
    • /
    • 2011
  • The empirical correlations for the prediction of penetration height of liquid jet in crossflow are reviewed and classified in this study. Around thirty different correlations had been proposed by many investigators. It has generally known that the penetration height of a liquid jet in a cross-flow is a function of the liquid to air momentum flux ratio and the normalized downstream distance from the injector. However, several researchers incorporated the Weber number, liquid-to-water or air viscosity ratio, pressure ratio or Reynolds number, temperature ratio in the empirical correlations. The existing correlations can be grouped as correlations in a power-law, logarithmic, and exponential forms, respectively. Correlations in a power-law form can be further classified as three groups such as basic form, Weber number form and other parameters form. It should be pointed out that correlations in a logarithmic form in terms of Weber number or any other parameters could not be found. Universal correlation has still not been established due to the significant discrepancies between various correlations suggested to date. Several of the studies reported the significant discrepancies of predicted values by the existing correlations. The possible reasons for discrepancies will be summarized as measurement technique, assumptions made in defining terms in the liquid to air momentum flux ratio, difficulties in defining the boundaries of the liquid jets, and nozzle/injector geometry. Evaluation of validity for the correlations proposed recently by several investigators is essentially required. Those include eight power-law forms, two logarithmic forms, and one exponential form.

Limit Span/Depth Ratio for Indirect Deflection Control in Reinforced Concrete Flexural Members (철근콘크리트 휨부재의 처짐 간접제어를 위한 한계 지간/깊이-비 연구)

  • Choi, Seung-Won;Kim, Woo
    • KSCE Journal of Civil and Environmental Engineering Research
    • /
    • v.31 no.1A
    • /
    • pp.35-41
    • /
    • 2011
  • In concrete structural design provisons, two methods are normally provided to control deflection; direct method and indirect method. It is more efficient to use the indirect deflection control by which the span/depth ratio is limited not to exceed an allowable deflection limit. Because actual deflections are affected by many causes, it is complicated to evaluate actual deflections. In this study, limit span/depth ratios are derived from the deflection calculated directly at the serviceability limit state in RC members. The deflection is obtained from using average curvature, which depends on materials model used. The main variables examined are tension stiffening effect, concrete strength, cross section size and compressive steel ratio. It could be appeared that more analytical consistency is secured to use the 2nd order form of tension stiffening effect. And the limit span/depth ratio is dependent on material strength, tensile and compressive steel ratio but it is independent on cross-section size.

The Design Simulation of the Levitation Magnet for the Urban Transit Maglev as the Running Vehicle on Curved Line(60mR) (자기부상열차의 곡선주로(60mR) 주행 시를 고려한 부상용 전자석 설계 Simulation)

  • Kim, Bong-Seop
    • Proceedings of the KIEE Conference
    • /
    • 2002.07b
    • /
    • pp.682-684
    • /
    • 2002
  • There is much room for consideration that the magnet design of UTM. When the vehicle runs 60mR curved line on test track, the ratio of cross section area changed to cross the magnet pole and rail. The ratio is reduced about 20% of the total magnet on one bogie. Therefor, magnet current is increased about 3.5A to maintain constant air gap. This paper suggest to margin of the magent design is 1.1 rather than rated levitation force.

  • PDF

A self-localization algorithm for a mobile robot using perspective invariant

  • Roh, Kyoung-Sig;Lee, Wang-Heon;Kweon, In-So
    • 제어로봇시스템학회:학술대회논문집
    • /
    • 1996.10b
    • /
    • pp.920-923
    • /
    • 1996
  • This paper presents a new algorithm for the self-localization of a mobile robot using perspective invariant(Cross Ratio). Most of conventional model-based self-localization methods have some problems that data structure building, map updating and matching processes are very complex. Use of the simple cross ratio can be effective to the above problems. The algorithm is based on two basic assumptions that the ground plane is flat and two parallel walls are available. Also it is assumed that an environmental map is available for matching between the scene and the model. To extract an accurate steering angle for a mobile robot, we take advantage of geometric features such as vanishing points(V.P). Point features for computing cross ratios are extracted robustly using a vanishing point and the intersection points between floor and the vertical lines of door frames. The robustness and feasibility of our algorithms have been demonstrated through experiments in indoor environments using an indoor mobile robot, KASIRI-II(KAist SImple Roving Intelligence).

  • PDF

A comparative study for bending of cross-ply laminated plates resting on elastic foundations

  • Zenkour, Ashraf M.
    • Smart Structures and Systems
    • /
    • v.15 no.6
    • /
    • pp.1569-1582
    • /
    • 2015
  • Two hyperbolic displacement models are used for the bending response of simply-supported orthotropic laminated composite plates resting on two-parameter elastic foundations under mechanical loading. The models contain hyperbolic expressions to account for the parabolic distributions of transverse shear stresses and to satisfy the zero shear-stress conditions at the top and bottom surfaces of the plates. The present theory takes into account not only the transverse shear strains, but also their parabolic variation across the plate thickness and requires no shear correction coefficients in computing the shear stresses. The governing equations are derived and their closed-form solutions are obtained. The accuracy of the models presented is demonstrated by comparing the results obtained with solutions of other theories models given in the literature. It is found that the theories proposed can predict the bending analysis of cross-ply laminated composite plates resting on elastic foundations rather accurately. The effects of Winkler and Pasternak foundation parameters, transverse shear deformations, plate aspect ratio, and side-to-thickness ratio on deflections and stresses are investigated.