• International Journal of Fluid Machinery and Systems
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• v.2 no.4
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• pp.383-391
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• 2009

Vibrations at different frequencies with a different intensity as well as a pressure pulsation with different parameters are two phenomena which can be observed at different water turbines. Due to the vibration and the pressure pulsation some restrictions of water turbine operation range are applied. Similar problems with the efficiency level in a wide water turbine operation range are the basic problems which are solved for ages. A theoretical and practical solution of the above mentioned problems is very much time and money consuming. The paper describes a new theoretical solution of the excitation and pressure pulsation decrease as well as extension of the operational range with high efficiency level. The new concept to decrease the vibrations and pressure pulsations is based on a heterogeneous runner blade geometry generation. The new concept of the runner geometry design was numerically tested at a low specific speed pump turbine, see Fig. 1, and basic points of the concept are presented in this paper.

• Journal of Navigation and Port Research
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• v.31 no.3 s.119
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• pp.223-228
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• 2007

In recent trends of the enlargement and specialization, container ship, LNCG, PCC and passenger ship which have relatively large hull and superstructure above the water line, are already being operated in the world It is very important information for the safety operation of these vessels to estimate the ship's performance under the specific wind condition while berthing, unberthing or low-speed sailing. In this paper, the effect of wind force and moment acting on the training ship HANNARA is investigated by using the numerical calculations. The results of drift angle and counter rudder angle with the relative wind direction and force, the critical wind velocity with the ratio of wind velocity and ship's speed and maximum heeling angle with the wind velocity are shown The presented results can be applied directly to T/S HANNARA in berthing maneuver and avoiding typhoons, and utilized as an educational materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.407.1-407.1
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• 2016

Electrochromism is defined as a phenomenon which involves persistently repeated change of optical properties between bleached state and colored state by simultaneous injection of electrons and ions, sufficient to induce an electrochemical redox process. Due to this feature, considerable progress has been made in the synthesis of electrochromic (EC) materials, improvements of EC properties in EC devices such as light shutter, smart window and variable reflectance mirrors etc. Among the variable EC materials, solid-state inorganics in particular, metal oxide semiconducting materials such as nickel oxide (NiO) have been investigated extensively. The NiO that is an anodic EC material is of special interest because of high color contrast ratio, large dynamic range and low material cost. The high performance EC devices should present the use of standard industrial production techniques to produce films with high coloration efficiency, rapid switching speed and robust reversibility. Generally, the color contrast and the optical switching speed increase drastically if high surface area is used. The structure of porous thin film provides a specific surface area and can facilitate a very short response time of the reaction between the surface and ions. The large variety of methods has been used to prepare the porous NiO thin films such as sol-gel process, chemical bath deposition and sputtering. Few studies have been reported on NiO thin films made by using sol-gel method. However, compared with dry process, wet processes that have the questions of the durability and the vestige of bleached state color limit the thin films practical use, especially when prepared by sol-gel method. In this study, we synthesis the porous NiO thin films on the fluorine doped tin oxide (FTO) glass by using sputtering and anodizing method. Also we compared electrical and optical properties of NiO thin films prepared by sol gel. The porous structure is promised to be helpful to the properties enhancement of the EC devices.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.12
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• pp.67-75
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• 1999

In this paper, we present an ASIC(Application Specific Integrated Circuit) design of wavelet transform filter Wavelet transform is used in lots of application fields which include image compression, because it has an excellent energy compaction. The operation characteristic and performance of wavelet transform filter are analyzed by using verilog-HDL(Hardware Description Language). In this paper, the designed wavelet transform filter uses line memory to improve data processing rate. Generally, when it reads and writes data of DRAM by using Fast Page Mode, input and output processing is very fast in horizontal direction but substantially slow in vertical direction. The use of line memory solves this low speed processing problem. As a result, though the size of the chip is getting larger, processing time for an image frame becomes 4.66ms. Generally, since the limit of 1 frame processing time on the data of TV video is 33ms, so it is appropriate for TV video.

• Journal of environmental and Sanitary engineering
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• v.17 no.3
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• pp.99-109
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• 2002

Charcoal $tube/CS_2$ method are more popularly used than any other in the measurement of the working environment for the exposure evaluation of organic solvent, but it is some weak points that the lower accuracy can be obtained on the polar materials and within the range of the low concentration. Thus solvent desorption method has been developed to make accuracy higher and to overcome some weak points. However, because of high price of adsorption tube for thermal desorption and the short of study on its application to the working environment, it is not popularly used in the domestic industrial hygiene fields. This dissertation aims to develop thermal desorption and adsorption tubes for measuring organic solvents in the working environment, by comparing and analyzing breakthrough condition and adsorption capacity with ACF. Specific surface area of ACF used in this study is wider than the one of AC and micropore of ACF related with adsorption has been developed, and adsorption velocity and adsorption amount are very excellent by linking a pore of surface and an inside well into micropore. 1. Result of analysis on physical characteristics of adsorbent, the specific surface area of ACF was 1.3 times higher than that of AC. Distribution ratio of micropore related to adsorption was 94% on ACF and AC. Result of SEM, micropore of the AC is opened to the surface. In contrast, ACF shows that extremely fast adsorption speed. Because of micropore are exposed on the surface and penetrate through each other. 2. Breakthrough characteristics of adsorbents was not different from slop of breakthrough curve. The effluent concentration reaches 10% of initial concentration($C_{out}/C_{in}=0.1$, break point) of ACF was 30~316min longer than that of AC. Therefore, the adsorption capacities of ACF was 1.1~4.6 times higher than that of AC. ACF can be used as a proper adsorbent for measurement of organic solvent.

• Structural Engineering and Mechanics
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• v.70 no.2
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• pp.169-178
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• 2019

The replacement of damaged components is an important task for long-span bridges. Conventional strategy for component replacement is to close the bridge to traffic, so that the influence of the surrounding environment is reduced to a minimum extent. However, complete traffic interruption would bring substantial economic losses and negative social influence nowadays. This paper investigates traffic control technologies without interruption for component replacement of long-span bridges. A numerical procedure of traffic control technologies is proposed incorporating traffic microsimulation and site-specific data, which is then implemented through a case study of cable replacement of a long-span cable-stayed bridge. Results indicate traffic load effects on the bridge are lower than the design values under current low daily traffic volume, and therefore cable replacement could be conducted without traffic control. However, considering a possible medium or high level of daily traffic volume, traffic load effects of girder bending moment and cable force nearest to the replaced cable become larger than the design level. This indicates a potential risk of failure, and traffic control should be implemented. Parametric studies show that speed control does not decrease but increase the load effects, and flow control using lane closure is not effectual. However, weight control and gap control are very effective to mitigate traffic load effects, and it is recommended to employ a weight control with gross vehicle weight no more than 65 t or/and a gap control with minimum vehicle gap no less than 40 m for the cable replacement of the case bridge.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.317-327
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• 2012

The average specific cake resistance, the most important indicator for cake filtration and solid-liquid separation, is measured by filtration experiment. But the exact value is difficult to measure because of the other influences such as sedimentation during filtration. This study, a little more stable method named filtration-permeation is proposed for measuring average specific cake resistance. The filtration-permeation is composed of permeation of particle eliminated water through pre-formed cake by filtration. Using 1 wt% calcium carbonate suspension, the filtration-permeation experiments were performed for 8 kinds of filter media at the conditions of 0.5 atm and 0.2 atm, 1 and 3 sheets of filter media. At each specific condition, three to five times filtration-permeation were accomplished. As a result, stable permeation speed is measured. According to this experimental result, the characteristics of permeation and the effect of sedimentation are analyzed with Ruth's equation. The one way analysis of variance (one way ANOVA) is applied to the average specific cake resistances of filtration and permeation obtained with the selected three kinds of filter media. The average specific cake resistances between 0.5 atm and 0.2 atm by filtration do not distinguished, but those by permeation is perfectly distinguished. The experimental results during permeation have a very narrow distribution than that measured during filtration. The analysis of filtration experiments, it was verified that the resistance of filter medium by traditional method is of no significance. Finally, the migration of small particles through the medium composed of fiber glass at low pressure was studied.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.6
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• pp.599-605
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• 2013

The characteristics of centrifugal pump performance according to fluid viscosity change were studied experimentally. A small volute pump with low specific speed was tested by changing the viscosity of an aqueous solution of sugar and glycerin, which is considered a Newtonian fluid. After finishing the test, the total head, shaft horsepower, and pump efficiency were compared with those of a water pump. The results are summarized as follows: (1) when the fluid viscosity is increased, the shut-off head shows very little change but the total head decreases gradually as the flow increases, and this makes the H-Q curve leaning rapidly, and (2) when the fluid viscosity is increased, the shaft horsepower shows very little change at the shutoff condition; however, the shaft horsepower increases more rapidly with an increase in the flow and viscosity.

• International journal of advanced smart convergence
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• v.10 no.4
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• pp.241-255
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• 2021

The human auricle is the first part to receive sound from the outside. In this part, the frequency range of human recognizable form is divided and organized. In this study, we propose modeling by applying a single sound source to the surface of the human auricle. This means that when the sound pressure of a low frequency (low frequency) sound enters the pinna, the impedance felt at the tip of a part of the non-linear surface of the pinna is mainly due to the tensile force at the end of the part of the non-linear surface of the pinna. By expressing the situation of moving at a very small speed, the characteristic impedance of the pinna was confirmed to be negative infinity, and it was also confirmed that the speed at the tip of a part of the non-linear surface of the pinna was 0 in the anti-resonance state. It was found that the wave propagation phenomenon that determines the characteristics of the filter is determined by how large the wavelength, kL, is compared to the length of the tip of a part of the non-straight surface of the pinna. Humans first receive sounds from outside through their ears. The auricle is non-linear and has a curved shape, and it is known that it analyzes frequencies while receiving external sounds. The human ear has an audible frequency range of 20Hz - 20,000Hz. Through the study, we applied the characteristics of the notch filter to hypothesize that the human audible frequency range is separated from the auricle, and applied filter theory to analyze it, and as a result, meaningful results were obtained. The curved part and the inner part of the auricle function as a trumpet, collecting sounds, and at the same time amplifying the weak sound of a specific band. The point was found and the shape of the envelope detected in the auricle was found. Selectivity for selecting sounds coming from the outside is the formula of the pinna that implements the function of Q. The function of distinguishing human-recognizable sound from the pinna from low to high through frequency analysis is performed in the pinna, and the 2-3kHz area, where human hearing threshold is the most sensitive, is also the acoustic impedance of the most recessed area of the pinna. It can be seen that starting from.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.68-73
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• 2019

We proposed a method to convert the CO2 emission data of vehicles collected from the chassis dynamometer test from distance unit to energy unit which generally measured from the engine dynamometer tests. In the future, if engine dynamometer tests are limited, it is expected to be applied as an alternative method to calculate CO2 emission based on energy unit through the chassis dynamometer test. At this moment, engine efficiency is required and the test mode average efficiency should be used to improve the accuracy, not the result derived from specific speed and load conditions. Also, this method was applied to foreign data and the results were within 0.2%. However, CO, NOx and THC which have very low emission characteristics except CO2, are limited by the method proposed in this study and need to be considered separatively.