• Magazine of the Korea Concrete Institute
• /
• v.5 no.4
• /
• pp.123-134
• /
• 1993

A rapid progress has been made over last decade in the state-of-the-art earthquake structura1 engineering towards a better understanding of both the earthqauke ground motion and structural response. These efforts seek to ensure that there will be no serious injury or loss of life in the event of earthquake, and that structures can be built at minimum cost. The design of structures in general, concrete structures in particular, to resist strong ground input motions is not a simple matter, and analytical models for such structures must be developed from a design perspective that accounts for the complexities of the structural responses. The primary obj ective of earthquake structural engineering research is to ensure the safety of structures by understanding and improving a design methodology. Ideally, this would require the development of an analytical model related to a design methodology that ensures a ductile performance. For the accurate assessment of the adequacy of analytically developed model, experiments conducted to study the inplane inelastic cyclic behavior of structures should verify the analytical approach. The fundamental goal of this paper is to present and demonstrate experimentally verified analytical methods that provide the adequate degree of safety and confidience in the behavior of reinforced concrete structural components. This study further attempts to extend the developed modeling techruque for use by practicing structural engineers for both the analysis and design.Plication of the relaxed diaphragm through left thoracotomy was done and result was excellent as seen on Fig. 5. Cause of eventration of the left hemidiaphragm was due to paralysis of the left phrenic nerve which was tested during thoracotomy.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.3
• /
• pp.52-59
• /
• 2001

In this study, a technique has been developed to analyze the performance of the launching system using a gas generator of solid propellant. The physical model which described the thermodynamic behaviors of all launching devices from gas generator to canister and the dynamic behavior of missile was established, applying the empirical coefficients in the heat loss model. The processes of combustion, flow, and heat transfer inside the chamber of gas generator and the launching system were simulated by numerical method. The theoretical analysis guided the optimal design of gas generator and system, which made the launching system satisfy the requirements of good performance and high reliability.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2000.11a
• /
• pp.421-424
• /
• 2000

This paper investigates the characteristics of analytical models in prediction of sound transmission loss for the multi-layered panels with high density mineral wools. The results show that the sandwich model is more adequate to account for sound insulation performance of those panels than the poro-elastic model. In order to improve STC(Sound Transmission Class), the effect of fiber directions of mineral wools is examined, analytically and experimentally. From the comparison of the measurements with the predictions, it is evident that the vertical fiber directions of mineral wools enhance STC value up to 6 dB, compared to that of the horizontal fiber directions.

• Ocean and Polar Research
• /
• v.25 no.1
• /
• pp.63-74
• /
• 2003

The build-up of the heat field in shallow coastal water due to a point source has been investigated using an analytical solution of a time-integral form derived by extending the solutions by Holley(1969) and also presented in Harleman (1971). The uniform water depth is assumed with non-isotropic turbulent dispersion. The alongshore-flow is assumed to be uni-directional, spatially uniform and oscillatory. Due to the presence of the oscillatory alongshore-flow, the heat build-up occurs in an oscillatory manner, and the excess temperature thereby fluctuates in that course and even in the quasi-steady state. A series of calculations reveal that proper choices of the decay coefficient as well as dispersion coefficients are critical to the reliable prediction of the excess temperature field. The dispersion coefficients determine the absolute values of the excess temperature and characterize the shoreline profile, particularly within the tidal excursion distance, while the decay coefficient determines the absolute value of the excess temperature and the convergence rate to that of the quasi-steady state. Within the e-folding time scale $1/k_d$ (where $k_d$ is the heat decay coefficient), heat build-up occurs more than 90% of the quasi-steady state values in a region within a tidal excursion distance (L), while occurs increasingly less the farther we go to the downstream direction (about 80% at 1.25L, and 70% at 1.5L). Calculations with onshore and offshore discharges indicate that thermal spreading in the direction of the shoreline is reduced as the shoreline constraint which controls the lateral mixing is reduced. The importance of collecting long-term records of in situ meteorological conditions and clarifying the definition of the heat loss coefficient is addressed. Interactive use of analytical and numerical modeling is recommended as a desirable way to obtain a reliable estimate of the far-field excess temperature along with extensive field measurements.

• Journal of the Korean Society for Railway
• /
• v.19 no.2
• /
• pp.124-134
• /
• 2016

Research on low height noise barriers installed adjacent to railways to reduce the height of the noise barrier has actively progressed in many countries except Korea. The performance of low height noise barriers is evaluated to identify barrier acoustic characteristics using a scale model of the barrier in the present research. As shown in the experimental results, if it is considered the installation of 'ㄱ' type noise barrier, sound absorption material should be installed on both the top and the vertical surfaces of the barrier to improve insertion loss. Also, an analytical method such as the boundary element method, rather than a simple empirical equation, is required to evaluate the insertion loss of the barrier. In addition, noise level increase in passenger position is very small if a barrier with sound absorption material is installed. Finally, the two dimensional boundary element method is implemented to predict the acoustic characteristics of the low height barrier; the possibility of the application is confirmed from a comparison of the results of measurements and predictions.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.2
• /
• pp.513-525
• /
• 2018

A 3 dimensional numerical analysis for shield TBM tunnel should take into account various characteristics of the shield TBM excavation, such as gap, tail void, segment installation, and backfill injection. However, analysis method considering excavation characteristics are generally mixed with various method, resulting in concern of consistency and reliability degradation of the analytical results. In this paper, a parametric study is carried out by using actually measured ground settlement data on various methods that can be used for 3 dimensional numerical analysis of shield TBM tunneling. As a result, we have analyzed and arranged an analytical method to predict similarly the behavior of ground settlement and tunnel face pressure at the design stage. Skin plate pressure, backfill pressure and soil model have been identified as the most significant influences on the ground settlement. The grout pressure model is considered to be applicable when there is no volume loss information on the excavated ground, such as seabed tunnels, or when it is important to identify the behavior around a tunnel, such as surface settlement as well as face pressure. And it is considered that designers can use these guidelines as a base material to perform a reasonable 3 dimensional numerical analysis that reflects the ground conditions and the features of the shield TBM tunneling.

• Journal of the Korean Society for Nondestructive Testing
• /
• v.33 no.4
• /
• pp.336-341
• /
• 2013

In this paper, the design concept of a low-temperature vacuum blackbody was described, and thermophysical model of the blackbody was numerically evaluated. Also the working performance of low-temperature vacuum blackbody was evaluated using infrared camera system. The blackbody system was constructed to operate under high-vacuum conditions ($2.67{\times}10^{-2}$ Pa) to reduce temperature uncertainty, which is caused by vapor condensation at low temperatures usually below 273 K. In addition, both heat sink and heat shield including cold shield were installed around radiator to prevent heat loss from the blackbody. Simplified mathematical model of blackbody radiator was analyzed using modified Stefan-Boltzmann's rule. The infrared radiant performance of the blackbody was evaluated using infrared camera. Based on the results of measurements, and simulation, temperature stability of the low-temperature vacuum blackbody demonstrated that the blackbody system can serve as a highly stable reference source for the calibration of an infrared optical system.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.22 no.1
• /
• pp.53-66
• /
• 1980

The research work is concerned with the analytical and experimental studies on the heat transfer phenomenon around the underground concrete digester used for biogas production Systems. A mathematical and computational method was developed to estimate heat losses from underground cylindrical concrete digester used for biogas production systems. To test its feasibility and to evaluate thermal parameters of materials related, the method was applied to six physical model digesters. The cylindrical concrete digester was taken as a physical model, to which the model,atical model of heat balance can be applied. The mathematical model was transformed by means of finite element method and used to analyze temperature distribution with respect to several boundary conditions and design parameters. The design parameters of experimental digesters were selected as; three different sizes 40cm by 80cm, 80cm by 160cm and l00cm by 200cm in diameter and height; two different levels of insulation materials-plain concrete and vermiculite mixing in concrete; and two different types of installation-underground and half-exposed. In order to carry out a particular aim of this study, the liquid within the digester was substituted by water, and its temperature was controlled in five levels-35。 C, 30。 C, 25。 C, 20。C and 15。C; and the ambient air temperature and ground temperature were checked out of the system under natural winter climate conditions. The following results were drawn from the study. 1.The analytical method, by which the estimated values of temperature distribution around a cylindrical digester were obtained, was able to be generally accepted from the comparison of the estimated values with the measured. However, the difference between the estimated and measured temperature had a trend to be considerably increased when the ambient temperature was relatively low. This was mainly related variations of input parameters including the thermal conductivity of soil, applied to the numerical analysis. Consequently, the improvement of these input data for the simulated operation of the numerical analysis is expected as an approach to obtain better refined estimation. 2.The difference between estimated and measured heat losses was shown to have the similar trend to that of temperature distribution discussed above. 3.It was found that a map of isothermal lines drawn from the estimated temperature distribution was very useful for a general observation of the direction and rate of heat transfer within the boundary. From this analysis, it was interpreted that most of heat losses is passed through the triangular section bounded within 45 degrees toward the wall at the bottom edge of the digesten Therefore, any effective insulation should be considered within this region. 4.It was verified by experiment that heat loss per unit volume of liquid was reduced as the size of the digester became larger For instance, at the liquid temperature of 35˚ C, the heat loss per unit volume from the 0. 1m$^3$ digester was 1, 050 Kcal/hr m$^3$, while at for 1. 57m$^3$ digester was 150 Kcal/hr m$^3$. 5.In the light of insulation, the vermiculite concrete was consistently shown to be superior to the plain concrete. At the liquid temperature ranging from 15。 C to 350 C, the reduction of heat loss was ranged from 5% to 25% for the half-exposed digester, while from 10% to 28% for the fully underground digester. 6.In the comparison of heat loss between the half-exposed and underground digesters, the heat loss from the former was fr6m 1,6 to 2, 6 times as much as that from the latter. This leads to the evidence that the underground digester takes advantage of heat conservation during winter.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2008.11a
• /
• pp.199-202
• /
• 2008

This paper presents a mathematical-physical model to predict the performance of a gas pusher used as a separation system powered by a gas generator. The empirical coefficients of heat loss and friction were determined from experiments. Based on the grain configuration of the gas generator, the analytical approach of combustion, flow and movement of a piston inside the chamber of a gas generator and a gas pusher was simulated by numerical method. The prediction method developed can be usefully applied to the design of separation mechanism systems.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.23 no.4
• /
• pp.29-34
• /
• 2023

A clear and efficient design method for a microstrip-to-waveguide inline transition, which is based on an analytical model, is presented. The transition consists of three parts: a microstrip-to-SIW transition, a dielectric-loaded waveguide with substrate-height, and a stepped-height waveguide. The shape of the transitional structure is formed for impedance matching. Two equivalent type0s of dielectric-loaded transitional structures are proposed. The design method is applicable to any size of the waveguide, but a design method of two Ka-band transitions is demonstrated. The proposed transitions, in a back-to-back configuration, have less than 1.2 dB insertion loss and more than 15 dB return loss from 29.8 GHz to 38.2 GHz.