• Journal of Energy Engineering
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• v.17 no.1
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• pp.31-37
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• 2008

At present, the target amount of demand-side management and investment cost of EE (Energy Efficiency) program, which consists of high-efficiency appliances, has been estimated simply by the diffusion function based on the real historical data in the past or last year. In the internal and external condition, the penetration amount of each appliance has been estimated by Bass diffusion model which is expressed by time and three coefficients. And enough acquisition of real historical data is necessary for reasonable estimation of coefficients. In energy efficiency, to estimate the target amount of demand-side management, the penetration amount of each appliance should be primarily forecasted by Bass diffusion model in Korea. On going programs, however, lightings, inverters, vending machine and motors have a insufficient real historical data which is a essential condition to forecast the penetration amount using a Bass diffusion model due to the short period of program progress. In other words, the forecast of penetration amount may not be exact, so that it is necessary for the method of forecast to apply improvement of method. In this paper, the penetration amount of high-efficiency appliances is forecasted by Bass, virtual Bass, Logistic and Lawrence & Lawton diffusion models to analyze the diffusion progress. And also, by statistic standards, each penetration is compared with historical data for model suitability by characteristic of each appliance. Based on the these result, in the forecast of penetration amount by diffusion model, the reason for error occurrence caused by simple application of diffusion model and preferences of each diffusion model far a characteristic of data are analyzed.

• Laser Solutions
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• v.4 no.2
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• pp.13-19
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• 2001

When a high-power laser beam is irradiated on the surface of material, it is well known that a cavity, called a keyhole induced by the pressure action of the vapor plume, is generated in the molten material. This paper describes the interaction between a pulsed CO$_2$ laser beam and water. The laser-beam is used to generate and maintain a conical depression in the water surface similar to the keyhole created during laser penetration welding. Experimental results show that the depth of laser-beam penetration is limited by hydrodynamic instability. The instability of the surface cavity can be understood by the capillary instability of a hollow jet. Theoretical computation of the steady keyhole shape has been performed. modifying the model suggested by Andrews et al. (1976). The model predicts the qualitative behavior of the keyhole but significantly underestimates the average diameter.

• Journal of ILASS-Korea
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• v.22 no.4
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• pp.169-174
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• 2017

The objective of this study was to verify the experimental and numerical results of spray evolution injected from different types of the nozzle-hole geometries. Spray visualization was taken by high speed camera under the different conditions. For the simulations of spray tip penetration, turbulence, evaporation and break-up model were applied K-zeta-f, Dukowicz and Wave model, respectively. Also, the prediction accuracy of spray tip penetration was increased by varying the spray cone angle. At the same time, the results of this work were compared in terms of spray tip penetration, and SMD characteristics. The numerical results of spray evolution process and spray tip penetration showed good agreement with experimental one.

• Tribology and Lubricants
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• v.36 no.5
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• pp.290-296
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• 2020

When two layers of carbon nanotube (CNT) arrays are loaded to mate, the free ends of individual CNTs come into contact at the interface of the two layers. This leads to a higher contact resistance due to a smaller contact region. However, when the free CNT ends of one array penetrate into the mating array, the contact region increases, effectively lowering the contact resistance. To explore the penetration of mating CNTs, we perform molecular dynamic simulations of a simple unit cell model, incorporating four CNTs in the lower array layer coupled with a single moving CNT on the upper layer. The interaction with neighboring CNTs is modelled by long-range carbon bond order potential (LCBOP I). The model structure is optimized by energy minimization through the conjugate gradient method. A NVT ensemble is used for maintain a room temperature during simulation. The time integration is performed through the velocity-Verlet algorithm. A significant vibrational motion of CNTs is captured when penetration is not available, resulting in a specific vibration mode with a high frequency. Due to this vibrational behavior, the random behaviors of CNT motion for predicting the penetration are confirmed under the specific gap distances between CNTs. Thus, the probability of penetration is examined according to the gap distance between CNTs in the lower array and the aspect ratio of CNTs. The penetration is significantly affected by the vibration mode due to the van der Waals forces between CNTs.

• Textile Coloration and Finishing
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• v.16 no.1
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• pp.48-52
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• 2004

Diffusion/penetration rates of finishing agents are not a major criterion in the design of low molecular weight finishing agents. However, in the case of polymeric finishing agents, high molecular weights result in large hydrodynamic volumes and diffusion/penetration of the finishing agent into the substrate may become a critical factor in the design of textile finishing agents. Thus the effect of the molecular weight of a model compound, polyethylene glycol, on its diffusion through a cellulose membrane or cotton fabric is studied. Diffusion experiments of polyethylene glycol of molecular weight 400, 1000, 2000, 4600, 8000, and 10000 through cellulose membrane or fabric was carried out in a glass U-tube diffusion apparatus and the half penetration times and the penetration coefficients were determined. Both the half penetration times and the penetration coefficients exhibited a significant change between molecular weight 2000 and 2500 as the molecular weight of polyethylene glycol increased, suggesting that there is a critical molecular weight above which diffusion/penetration becomes difficult. Based on this study on a model compound, it is suggested that polymeric textile finishing agents can be expected to exhibit similar behavior.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.6
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• pp.33-43
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• 2021

A60 class bulkhead penetration piece is a fire resistance system installed on a bulkhead compartment to protect lives and to prevent flame diffusion in a fire accident on a ship and offshore plant. This study focuses on the approximate optimization of the fire resistance design of the A60 class bulkhead penetration piece using a multi-island genetic algorithm. Transient heat transfer analysis was performed to evaluate the fire resistance design of the A60 class bulkhead penetration piece. For approximate optimization, the bulkhead penetration piece length, diameter, material type, and insulation density were considered discrete design variables; moreover, temperature, cost, and productivity were considered constraint functions. The approximate optimum design problem based on the meta-model was formulated by determining the discrete design variables by minimizing the weight of the A60 class bulkhead penetration piece subject to the constraint functions. The meta-models used for the approximate optimization were the Kriging model, response surface method, and radial basis function-based neural network. The results from the approximate optimization were compared to the actual results of the analysis to determine approximate accuracy. We conclude that the radial basis function-based neural network among the meta-models used in the approximate optimization generates the most accurate optimum design results for the fire resistance design of the A60 class bulkhead penetration piece.

• Journal of ILASS-Korea
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• v.5 no.2
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• pp.35-42
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• 2000

A number of atomization and droplet breakup models have been developed and used to predict the diesel spray characteristics. Of the many atomization and droplet breakup models based on the breakup mechanism due to aerodynamic liquid and gas interaction, four models classified as mathematical models, such as TAB, modified TAB, DDB, WB and one of the hybrid model based on WB and TAB models were selected for the assessment of prediction ability of diesel spray dynamics. The assessment of these models by using KIVA-II code was performed by comparing with the experimental data of spray tip penetration and sauter mean diameter(SMD) from the literature. It is found that the prediction of spray tip penetration and SMD by the hybrid model was only influenced by the initial parcel number. All the atomization and droplet breakup models considered here was strongly dependent on the grid resolution. Therefore it is important to check the grid resolution to get an acceptable results in selecting the models. At low injection pressure, modified TAB model could only give the good agreement with experimental data of spray tip penetration and both of modified TAB and DDB models were recommendable for the prediction of SMD. At high injection pressure, hybrid model could only give the good agreement with the experimental data of spray tip penetration and the prediction of all of the selected models did not match the experimental data. Spray tip penetration was increased with the increase the $B_1$ and the increase of $B_1$ did not affected the prediction of SMD.

• Journal of the Korean Physical Society
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• v.73 no.11
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• pp.1764-1773
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• 2018

A-PET is a quad-head PET scanner developed for use in small-animal imaging. The dimensions of its volumetric field of view (FOV) are $46.1{\times}46.1{\times}46.1mm^3$ and the gap between the detector modules has been minimized in order to provide a highly sensitive system. However, such a small FOV together with the quad-head geometry causes image quality degradation. The main factor related to image degradation for the quad-head PET is the mispositioning of events caused by the penetration effect in the detector. In this paper, we propose a precise method for modelling the system at the high spatial resolution of the A-PET using a LOR (line of response) based ML-EM (maximum likelihood expectation maximization) that allows for penetration effects. The proposed system model provides the detection probability of every possible ray-path via crystal sampling methods. For the ray-path sampling, the sub-LORs are defined by connecting the sampling points of the crystal pair. We incorporate the detection probability of each sub-LOR into the model by calculating the penetration effect. For comparison, we used a standard LOR-based model and a Monte Carlo-based modeling approach, and evaluated the reconstructed images using both the National Electrical Manufacturers Association NU 4-2008 standards and the Geant4 Application for Tomographic Emission simulation toolkit (GATE). An average full width at half maximum (FWHM) at different locations of 1.77 mm and 1.79 mm are obtained using the proposed system model and standard LOR system model, which does not include penetration effects, respectively. The standard deviation of the uniform region in the NEMA image quality phantom is 2.14% for the proposed method and 14.3% for the LOR system model, indicating that the proposed model out-performs the standard LOR-based model.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.2
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• pp.238-245
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• 2017

This paper deals with the scale effects of warhead on concrete penetration. We investigated the scale effects using finite element analysis and Young's penetration equation. As the scale of penetration test decreases, the strain rate effects of target increases, and then strength of concrete target increases. This means the residual velocity and penetration depth of warhead decreases as the test model size decreases. Young's penetration equations are transformed with various penetrator mass and scale cases as a function of scale ratio. Penetration distance and residual velocity are not simply changed by the geometric scaling law.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.89-99
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• 2001

In this study, the numerical analysis of piezocone penetration and dissipation tests has been conducted using the Modified Cam-Clay model, which is generally used in soil mechanics. The Modified Cam-Clay model and related mathematical equations in finite element derivation have been formulated in the Updated Lagrangian reference frame to take the large displacement and finite strain nature of piezocone penetration into consideration. The cone tip resistance, the pore water pressure, and the dissipation curve obtained from the finite element analysis have been compared and investigated with the experimental results from piezocone penetration test performed in Yangsan site. The numerical results showed good agreement with the experimental results; however, the better numerical simulation of the continuous and deep penetration needs further research.