• Journal of Educational Research in Mathematics
• /
• v.19 no.1
• /
• pp.123-142
• /
• 2009

Dynamic context is considered as a source for intuitive understanding on the calculus. The relation between the area under time-velocity graph and distance is the base of the dynamic contexts which are treated in the integral calculus. The fundamental theorem of calculus has originated in dynamic contexts. This paper investigated the fundamental theorem of calculus via the relation between the area under time-velocity graph and distance. And we analyzed mathematics textbooks and the understanding of students. Finally we suggest some proposal for the teaching of the fundamental theorem of calculus.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.19 no.2
• /
• pp.191-201
• /
• 2007

It was noted by the several researchers that the voltage outputs in response to a single yawed hot-wire sensor in a flow perpendicular to the axis deviate from the theoretical voltage output by King's law and Jorgensen's relation. This study noticed that the calibration coefficients of original Grande's method are not constant and fairly sensitive to the radial angle (${\alpha}_{R}$). For more accuracy, this study interpolated the parameters of the Grande relation as a function of radial angle and compared velocity components with ones by Jorgensen and original Grande relation in the calibration jet flow. Finally, as a test case, 3-dimensional turbulent flows of the inlet plane of 180 degree bend are measured and compared the velocity components by above three methods and showed the characteristics of the flows.

• The Bulletin of The Korean Astronomical Society
• /
• v.43 no.2
• /
• pp.35.2-35.2
• /
• 2018

Using the K-band Multi-object Spectrograph (KMOS) at the Very Large Telescope (VLT), the KMOS Redshift One Spectroscopic Survey (KROSS) has gathered integral-field data for ~800 star-forming galaxies at a redshift z~1, when the universe was roughly half its current age and forming the bulk of its stars. With spatially-resolved observations, KROSS reveals galaxies that are both gas-rich and highly turbulent. It is possible to derive the observed and baryonic Tully-Fisher (luminosity - rotation velocity) relations, thus constraining the mass-to-light ratios and total (luminous + dark) masses of the galaxies. This in turn highlights the dependence of the relation zero-point on the degree of rotational support of the galaxies (rotational velocity to velocity dispersion ratio). By degrading and analogously analysing integral-field data of hundreds of local galaxies from the Sydney-AAO Multi-object Integral-field Spectrograph (SAMI) survey, a robust comparison z=0 Tully-Fisher relation can also be derived, thus further constraining the luminous and dark mass growth of disk galaxies over the last 7 billions years. This unique comparison also reveals that systematic effects associated with sample selection and analysis methods are as large as the effects expected from cosmological evolution, and thus that most other comparisons employing heterogeneous data and/or methods can safely be ignored.

• Journal of Korean Society of Forest Science
• /
• v.107 no.2
• /
• pp.158-165
• /
• 2018

Reach-average velocity prediction in steep mountain streams is important for understanding fluvial processes and practical applications of erosion control in mountain streams. little studies have been conducted in reach-average velocity, but hydraulic researches have been carried out to examine the relationship between discharge and reach-average velocity in torrent reaches using a relatively large amount of discharge data. In this study, a total of 87 data were measured in 8 torrent reaches. Salt-dilution method was used to estimate discharge. Reach-average velocity was calculated from harmonic mean of travel time that were measured by salt-dilution technique. In order to exlpore the hydraulic relation, both discharge and velocity were non-dimensionalized by using $D_{50}$, $D_{84}$, ${\sigma}_{pro}$ and $IPR_{90}$. It also indicated that ${\sigma}_{pro}$ and $IPR_{90}$ were good variables as roughness height for develop the relationship between non-dimensional discharge and velocity in mountain streams. Generally, reach-average velocity could increase exponentially as discharge increases.

• Proceedings of the Korean Operations and Management Science Society Conference
• /
• 1996.04a
• /
• pp.137-140
• /
• 1996

This study investigated the length-tension and velocity-force relations of the torso erectors. A myoelectric based approach was used wherein a dynamic biomechanical model incorporating active and passive tissue charactreistics provided music kinematic estimates during controlled sagittal plan extension motions. A double linear optimization formulation from the literatured provided muscle tension estimates. The data supported a linear length-tension relation toward full flexion for both the erector spinae and latissimus muscles. Velocity trends agreed with that predicted by Hill's exponential relation. The results have implications for muscle tension estimation in biomechanical torso modeling, and suggest a possible low back pain injury mechanism.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• v.y2004m10
• /
• pp.59-63
• /
• 2004

In recent days. it is necessary to find environment-friendly way of diposing industrial waste and reclying system. So this study will analyze the property of Porous concrete improved by concrete waste powder and recycled lightweight aggregate and then suggest the ways of reclying. The method deals with experimenting unit weight of capacity. thermal conductivity, compression and ultrasonic pluse velocity. Considering the relation between ultrasonic pluse velocity and unit weight & thermal conductivity through the graph. the result of relation between ultrasonic pluse velocity and unit weight & thermal conductivity on the graph expessed their high interaction shown as direct proportion on the graph. Recycled Porous concrete merits lightweight and adiabatic. Therefore. we will expect that the current using ALC and Recycled Porous concrete has be similar thermal conductivity.

• The Bulletin of The Korean Astronomical Society
• /
• v.46 no.2
• /
• pp.43.4-43.4
• /
• 2021

One of the most promising secondary target programmes of DESI is the peculiar velocity survey, which will notably improve the measurements of cosmology parameters in the low-redshift universe. We use the Fundamental plane and Tully-Fisher relation as distance indicators to calculate peculiar velocities for DESI. This required additional observations to obtain spectra with sufficient quality to measure the velocity dispersions in the case of the fundamental plane, and to get off-centre redshift measurements to reconstruct the rotation curve in the case of the Tully-Fisher relation. However, we devised a clever strategy for suitable target galaxies, that takes advantage of the spare fibres of DESI to gather the required additional data without causing conflicts with the main survey programmes. We provide a brief overview of the preliminary results and success rate based on the first measurements obtained during survey validation as well as an outlook on expected improvements in the fσ₈ measurements once the survey has been completed.

• Journal of the Korean Society for Precision Engineering
• /
• v.2 no.1
• /
• pp.62-71
• /
• 1985

This is a study on the monitoring technique in tool failure and tool life by AE method. The relation between amplitude level of AE signal and flank wear width was studied by experiments. The relation between amplitude level of AE signal and tool life was also studied. As the result, it was observed that amplitude level of AE signal was only affected by cutting velocity. Amplitude level of AE signal was directly proportional to flank wear width and the increasing rate was related to cutting velocity. So, the relation between amplitude level of AE signal and tool life was represented as follow: $CT^n$ = $AE_{rms}$ where, n=0.35 C=9.5*$10^{-2}$

• The Bulletin of The Korean Astronomical Society
• /
• v.38 no.2
• /
• pp.46.1-46.1
• /
• 2013

WIth high accretion rate and low black hole mass, narrow line seyfert 1 galaxies (NLS1s) are an interesting sub-class of AGNs. To investigate whether NLS1s follow the same M-${\sigma}*$ relation as other AGNs, we selected a sample of 110 NLS1s at relatively low redshift z < 0.1 from SDSS DR7 by constraining the FWHM of Ha broad component, and determined their black hole masses. We measured stellar velocity dispersion of 65 objects which showed strong enough stellar lines in the SDSS spectra, while we adopted the ${\sigma}*$ measurements of 45 objects from Xiao et al. 2011. We find that NLS1s follow the M-${\sigma}*$ relation of active and inactive galaxies while there is a dependency due to the galaxy inclination, which probably cause rotational broadening of stellar absorption lines.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.31 no.6
• /
• pp.656-664
• /
• 2011

In this work, a numerical model is proposed for the relation between the magnitudes and the depth residual stress with the velocity of Rayleigh wave. Three cases, stress-free, uniform stress and layered stress, are investigated for the change tendency of the Rayleigh wave speed. Using the simulated signal with variation of residual stress magnitude and depth, investigation of the parameters for fitting residual stress and velocity change are performed. The speed change of Rayleigh wave shows a linear relation with the magnitude and an exponential relation with the depth of residual stress. The combination of these two effects could be used for the depth profile evaluation of the residual stress.