• Transactions of the Korean Society of Mechanical Engineers
• /
• v.11 no.2
• /
• pp.331-344
• /
• 1987

A numerical analysis has been conducted on the interaction of the thermal radiation and natural convection in a rectangular enclosure filled with a gray fluid. P-1 approximation is adopted for the radiative transfer and its application limit is examined. Considered are the Stark number effect, the optical thickness effect and the wall emissivity effect on the flow and heat transfer characteristics. As the Stark number increase or the optical thickness decreases, the boundary layer thickness and the flow velocity increase. Transition to turbulence is retarded with the increase of the radiation effect. When the optical thickness is one, the radiation effect is negligible for the Stark numbers larger than 10.

• Journal of Advanced Marine Engineering and Technology
• /
• v.19 no.2
• /
• pp.10-19
• /
• 1995

Heat trnasfer for absorbing and emitting media in laminar layer along the cylinders has been analyzed. Governing equation are transformed to local nonsimilarity equations by the dimensional analysis. The effects of the Stark number, Prandtl number, Optical radius and wall emissivity are mainly investigated. For the formal solution a numerical integration is performed and the results are compared with those obtained by P-1 and P-3 approximation. The results show that boundary layers consist of conduction-convection-radiation layer near the wall and convection-radiation layer far from the wall. As the Stark number of wall emissivity increases the local radiative heat flux is increased. The Pradtl number or curvature variations do not affect the radiative heat flux from the wall, but The Prandtl number or wall emissivity variations affect the conduction heat flux. Consequently the total heat flux from the wall are affected by the Prandtl number or wall emissivity variation.

• Journal of the Korean Mathematical Society
• /
• v.52 no.5
• /
• pp.907-928
• /
• 2015

We show in many cases that the Siegel-Ramachandra invariants generate the ray class fields over imaginary quadratic fields. As its application we revisit the class number one problem done by Heegner and Stark, and present a new proof by making use of inequality argument together with Shimura's reciprocity law.

• Journal of the Korean Chemical Society
• /
• v.41 no.5
• /
• pp.251-255
• /
• 1997

Fluorescence spectra and life time of $Eu^{3+}$ ion in borosilicate glass medium are measured. Electronic transitions of $Eu^{3+}$ ion in borosilicate glass medium are found to come from $5D0{\rightarrow}7FJ$(J=0, 1, 2, 3, 4) transitions of SL coupling system in $f^b$ electrons configuration. From the number of Stark sublevels in spetra, crystal field for $Eu^{3+}$ ion is also found to have the symmetric character of low symmetry order, $n{\leq}2$. The fraction and the number of components of life times were varied depending on the composition of $Eu^{3+}$ in borosilicate glasses, from which the binding condition between the $Eu^{3+}$ ion and anionic oxygen of borosilicate glass can be deduced.

• Bulletin of the Korean Mathematical Society
• /
• v.29 no.2
• /
• pp.201-204
• /
• 1992

After this discovery of lower bounds by Stark and Odlyzko, some people searched for number fields with relatively small discriminants. Also some others studied algorithms which will produce number fields with the smallest absolute value of the discriminant for a fixed degree n. However, this algorithmic approach does not work well if the extension degree n is greater than seven or eight. And it is not clear whether current computers can finish those algorithms in a reasonable amount of time for large n. So we are justified in our approach for this subject. In this paper we will report the results of our computations. Some number fields we found are better than previously known examples. Others are rediscoveries of known examples. However, there is theoretically nothing new in our approach to this subject.

• Applied Science and Convergence Technology
• /
• v.26 no.5
• /
• pp.118-128
• /
• 2017

The scope of this work is to determine and compare the effect of electron temperature ($T_e$) and number density ($N_e$) on the yield rate and concentration of reactive chemical species ($^{\bullet}OH$, $H_2O_2$ and $O_3$) in an argon, air and oxygen injected negative DC (0-4 kV) capillary discharge with water flow(0.1 L/min). The discharge was created between tungsten pin-to pin electrodes (${\Phi}=0.5mm$) separated by a variable distance (1-2 mm) in a quartz capillary tube (2 mm inner diameter, 4 mm outer diameter), with various gas injection rates (100-800 sccm). Optical emission spectroscopy (OES) of the hydrogen Balmer lines was carried out to investigate the line shapes and intensities as functions of the discharge parameters such as the type of gas, gas injection rate and inter electrode gap distances. The intensity ratio method was used to calculate $T_e$ and Stark broadening of Balmer ${\beta}$ lines was adopted to determine $N_e$. The effects of $T_e$ and $N_e$ on the reactive chemical species formation were evaluated and presented. The enhancement in yield rate of reactive chemical species was revealed at the higher electron temperature, higher gas injection rates, higher discharge power and larger inter-electrode gap. The discharge with oxygen injection was the most effective one for increasing the reactive chemical species concentration. The formation of reactive chemical species was shown more directly related to $T_e$ than $N_e$ in a flowing water gas injected negative DC capillary discharge.

• International Journal of Computer Science & Network Security
• /
• v.24 no.6
• /
• pp.200-206
• /
• 2024

Laser induced breakdown spectroscopy (LIBS) technique has been used for the elemental composition of the soils. In this technique, a high energy laser pulse is focused on a sample to produce plasma. From the spectroscopic analysis of such plasma plume, we have determined the different elements present in the soil. This technique is effective and rapid for the qualitative and quantitative analysis of all type of samples. In this work a Q-switched Nd: YAG laser operating with its fundamental mode (1064 nm laser wavelength), 5 nanosecond pulse width, and 10 Hz repetition rate was focused on soil samples using 10 cm quartz lens. The emission spectra of soil consist of Iron (Fe), Calcium (Ca), Titanium (Ti), Silicon (Si), Aluminum (Al), Magnesium (Mg), Manganese (Mn), Potassium (K), Nickel (Ni), Chromium (Cr), Copper (Cu), Mercury (Hg), Barium (Ba), Vanadium (V), Lead (Pb), Nitrogen (N), Scandium (Sc), Hydrogen (H), Strontium (Sr), and Lithium (Li) with different finger-prints of the transition lines. The maximum intensity of the transition lines was observed close to the surface of the sample and it was decreased along the axial direction of the plasma expansion due to the thermalization and the recombination process. We have also determined the plasma parameters such as electron temperature and the electron number density of the plasma using Boltzmann's plot method as well as the Stark broadening of the transition lines respectively. The electron temperature is estimated at 14611 °K, whereas the electron number density i.e. 4.1 × 10¹⁶ cm^-3 lies close to the surface.

• Korean Journal of Environment and Ecology
• /
• v.26 no.6
• /
• pp.960-969
• /
• 2012

This study aims to understand the time-based moving pattern and suggest management strategies through surveying the number of visitors from 7 a.m. to 7 p.m. for 3 days of each season in 3 key sites (Jeungsimsa district, Wonhyosa district and Jungmeorijae) of Mudeungsan Provincial Park. Majority of visitors who entered through Jeungsimsa district and Wonhyosa district visited the Mudeungsan provincial park from 9 a.m. to 2 p.m., and the number of enterers reached the peak from 10 to 11 in the morning. Majority of the visitors left the Mudeungsan provincial park from noon to 5 p.m.. The number of leavers showed the peak between 2 and 4 in the afternoon. Most of visitors who moved via Jungmeorijae from 11 a.m. to 3 p.m. climbed toward Jangbuljae or Jungbong or came down to Jeungsimsa district or Wonhyosa district. The number of enterers hit the highest from 11 a.m. to 1 p.m.. However, there was no stark difference in the time-based moving pattern of each season and days of week. The special intensive management such as providing visitor service, conducting a campaign and restoring the damaged land in concentrated site and time is needed for conserving natural resources and improving visitors satisfaction.

• Journal of Communications and Networks
• /
• v.12 no.2
• /
• pp.103-113
• /
• 2010

In this paper, a tradeoff between the total energy consumption-per-bit and the end-to-end rate under spatial reuse in wireless multi-hop network is developed and analyzed. The end-to-end rate of the network is the number of information bits transmitted (end-to-end) per channel use by any node in the network that is forwarding the data. In order to increase the bandwidth efficiency, spatial reuse is considered whereby simultaneous relay transmissions are allowed provided there is a minimum separation between such transmitters. The total energy consumption-per-bit includes the energy transmitted and the energy consumed by the receiver to process (demodulate and decoder) the received signal. The total energy consumption-per-bit is normalized by the distance between a source-destination pair in order to be consistent with a direct (single-hop) communication network. Lower bounds on this energy-bandwidth tradeoff are analyzed using convex optimization methods. For a given location of relays, it is shown that the total energy consumption-per-bit is minimized by optimally selecting the end-to-end rate. It is also demonstrated that spatial reuse can improve the bandwidth efficiency for a given total energy consumption-per-bit. However, at the rate that minimizes the total energy consumption-per-bit, spatial reuse does not provide lower energy consumption-per-bit compared to the case without spatial reuse. This is because spatial reuse requires more receiver energy consumption at a given end-to-end rate. Such degraded energy efficiency can be compensated by varying the minimum separation of hops between simultaneous transmitters. In the case of equi-spaced relays, analytical results for the energy-bandwidth tradeoff are provided and it is shown that the minimum energy consumption-per-bit decreases linearly with the end-to-end distance.

• Journal of the Society of Naval Architects of Korea
• /
• v.46 no.3
• /
• pp.313-314
• /
• 2009

To project military power, the paradigm of the modern warship aquisition has evolved with more large platform and high-technology equipment. For example, the Aegis combat system equipped warship is one of the most advanced and capable defense systems currently in use. Concurrently, if the warship attacked and disabled, it may worse the asymmetry of the battle field and it also depress the morale of the fleet. For that reason, to keep and protect few number of the big and high technology equipped warship from enemy is very important. At the present, the performance of unit weapon has enhanced remarkably. A Korean-built SS-209 class submarine, Lee Chun-ham, participated in Naval Exercise Tandem Thrust conducted in 1999, sink the target ship ex-USS Oklahoma by a single torpedo. USS Stark was struck on May 17, 1987, by two Exocet anti ship missiles and disabled. For this reason, susceptibility should be prior to vulnerability and recoverability. In this paper, deception ship which is small and chief but has very similar signatures to large and high technology equiped warship has conceptually studied by using systems engineering approach. And it may be a effective way to enhance the susceptibility of the key fighting power.