• 한국자동차공학회논문집
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• 제2권4호
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• pp.59-71
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• 1994

A multi-polynomial method is proposed to synthesize DRRD cam profiles. A cam lift duration s divided into 10 sections, each of them is expressed by a polynomial equation. 12 design variables are extracted from the cam profile displacement, velocity, and acceleration curves. Because all the design variables have physical meanings which are familiar to most cam designers, it is easy to imagine a profile shape from the design variables. The design envelope of the method is wide enough to be used in DRRD automotive cam designs. Polydyne cams, widely used in automotive engines, are included into the envelope. Unlike Polydyne cams, the method provides capability of wide velocity factor variations, which gives much flexibility in flat-faced tappet design. Area factor of profiles designed by the method can be increased 5-10% compared to those of Polydyne cams without increasing acceleration factor. The method is especially useful for cam profile optimizations.

• 오토저널
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• 제8권2호
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• pp.65-74
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• 1986

A computer program was developed to predict swirling steady axisymmetric turbulent flows by extending TEACH Code. It was applied to a reciprocating engine cylinder with a intake valve on the flat head. Flows were assumed to be steady and swirling. Effects of Reynolds number, the valve lift, and the swirl ratio on flow patterns and turbulence were investigated numerically. Flow patterns were reasonably predicted in comparison with experimental results. Length of the recirculation zone was shortened with increasing valve lifts and swirl ratios. Static pressure distributions show maximum value near the reattachment point of the incoming circular jet and minimum value near the maximum width of the valve attached recirculation zone.

• International Journal of Control, Automation, and Systems
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• 제3권1호
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• pp.87-99
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• 2005

We present in this paper the stabilization (tracking) with motion planning of the six independent configurations of a mini unmanned areal vehicle equipped with four streamlined rotors. Naturally, the yaw-dynamic can be stabilized without difficulties and independently of other motions. The remaining dynamics are linearly approximated around a small roll and pitch angles. It will be shown that the system presents a flat output that is likely to be useful in the motion generation problem. The tracking feedback controller is based on receding horizon point to point steering. The resulting controller involves the lift (collective) time derivative for what flatness and feedback linearization are used. Simulation tests are performed to progress in a region with approximatively ten-meter-buildings.

• International Journal of Aerospace System Engineering
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• 제2권2호
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• pp.40-43
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• 2015

A hybrid mesh based finite volume compressible flow code (PolySim) has been developed recently. Instead of the simple average method for the gradients of variables at each face, the volume average is applied for the calculation of the viscous flux. What is more, an improved Green Gauss method for the calculation of the gradient is also presented. These two techniques will improve both the accuracy and robustness of the code. The aerodynamic performance of this in-house cell centered code is examined by several widely-used bench-mark test cases. These cases include flows over flat plate and RAE 2822 etc. The comparisons on results between calculation and experiment are conducted. They show that the code can produce good numerical results which agree well with the corresponding experiment data.

• 패션비즈니스
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• 제12권2호
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• pp.72-86
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• 2008

This research focused on determining the brassiere preference index and wearing status of chinese ladies in their 20's living in the Shanghai region of China, to help Korean lingerie companies in their development of bras to successfully advance into the Chinese lingerie market. The main research tool of this research was various different surveys, and the results of the surveys were evaluated using the SPSS 12.0 for Window program. The results of the survey can be summarized as: 1) consciousness and satisfaction level of the body. The satisfaction level of the brest was proportionate to the size of the brassiere, thus, people showed higher level of satisfaction for cone-shaped, semi-circular shaped, prominent-shaped(exposing), lifted-shaped brest over flat-shaped brest. Concerning the relationship between the shape of the brest and the age of the customers, people under 22 years of age preferred flat-shaped, and those between 23-24 years of age preferring exposing and lifted brest, thus as females mature and get older, the size of their brest increases, thus having preference on more circular and lifted-shaped brest and bras. 2) Status of bra wearing in China When we look at the size of the bra in relation to the shape of the brest, those classified as having 'flat-shaped' brest showed a high proportion of A-cups, ranging from 75A, 70A and 80A, where as those of 'cone-shaped' brest represented high ration of B-cups, ranging from 75B, 75A and 80B. Majority of those classified as having 'semi-circular shaped' and 'prominent-shaped(exposing)' brest showed a high ration in the size 80 range. And vast majority of those classified into the 'lifted-shaped' brest group, were reported of having C-cup size bras. 3) Status of Bra Purchasing As people mature, the main reason behind choosing a bra was the actual design of the bra, where they emphasized the importance of aesthetic values. People classified as having 'flat-shaped' and 'cone-shaped' brest emphasized the importance of design and beauty, while those having 'semi-circular shaped,' 'prominent-shaped(exposing),' and 'liftedshaped' brest groups emphasized the importance of hygiene and the material(fabric) of the bra. This shows that when people have relatively smaller brest, they emphasize the importance of external appearance whereas when the size of the brest increases, they pay more attention to the function of the bra rather than the external appearance.

• 한국연소학회지
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• 제15권3호
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• pp.8-14
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• 2010

Fuel processing systems which convert fuel into rich gas (such as stream reforming, partial oxidation, autothermal reforming) need high temperature environment ($600{\sim}1,000^{\circ}$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1~5 kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas, mixture of natural gas & anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural gas & anode off gas as reformer fuel in the porous ceramic burner. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity. In particular, the blue surface flame is found to be very stable at a very lean equivalence ratio at heat capacity and different fuels. The exhausted NOx and CO measurement shows that the blue surface flame represents the lowest NOx and CO emissions since it remains very stable at a lean equivalence ratio.

• 한국재료학회지
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• 제23권8호
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• pp.453-461
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• 2013

Controlling the stick and slip motions of the contact lines in a confined geometry comprised of a spherical lens with a flat substrate is useful for manufacturing polymer ring patterns. We used a sphere on a flat geometry, by which we could control the interfaces of the solution, vapor and substrate. By this method, hundreds of concentric ring-pattern formations of a linear conjugated polymer, poly [2-methoxy-5-(2-thylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), were generated with excellent regularity over large areas after complete solvent evaporation. Subsequently, the MEH-PPV ring patterns played a role as a directed template to organize highly regular concentric rings of single-walled carbon nanotubes(SWCNTs); when a droplet of the SWCNT suspension in water was casted onto the prepared substrate, hydrophobic polymer patterns confined the water dispersed SWCNTs in between the hydrophilicized $SiO_2/Si$ substrate. As the solvent evaporated, SWCNT-rings were formed in between MEH-PPV rings with controlled density. Finally, we used a lift-off process to produce SWCNT patterns by the removal of a sacrificial polymer template with organic solvent. We also fabricated a field effect transistor using self-assembled SWCNT networks on a $SiO_2/Si$ substrate.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회B
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• pp.2181-2185
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• 2008

Fuel processing systems which convert HC fuel into $H_2$ rich gas (such as stream reforming, partial oxidation, auto-thermal reforming) need high temperature environment($600-1000^{\circ}C$). Generally, anode-off gas or mixture of anode-off gas and LNG is used as input gas of fuel reformer. In order to make efficient and low emission burner system for fuel reformer, it is necessary to elucidate the combustion and emission characteristic of fuel reformer burner. The purpose of this study is to develop a porous premixed flat ceramic burner that can be used for 1-5kW fuel cell reformer. Ceramic burner experiments using natural gas, hydrogen gas, anode off gas were carried out respectively to investigate the flame characteristics by heating capacity and equivalence ratio. Results show that the stable flat flames can be established for natural gas, hydrogen gas, anode off gas and mixture of natural & anode off gas as reformer fuel. For all of fuels, their burning velocities become smaller as the equivalence ratio goes to the lean mixture ratio, and a lift-off occurs at lean limit. Flame length in hydrogen and anode off gas became longer with increasing the heat capacity.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.711-714
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• 2002

At the lift-off condition, the combustion and Jet noise of launch vehicle produces a severe acoustic environment and the acoustic loads may be damaging to paylaod and equipments. Prediction of the acoustic environment is thus needed to support the load-resistive design and test-qualification of components. Currently, such a high frequency problem is usually dealt with by using the SEA technique, for which the assumptions should match reasonably well with the vibro-acoustic condition of system. The subsystems of SEA model was composed of 16 flat plates, 8 L-shaped beams, and 2 acoustic cavities. The frequency range was 400 Hz - 4 kHz considering the modal parameter. The experiment was performed in a high intensity acoustic chamber, in which the diffuse acoustic field was assured. By comparing the SEA analysis and the experiments, the error less than 5 dB was observed.

• 한국세라믹학회지
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• 제47권6호
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• pp.623-626
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• 2010

We synthesized ZnO nanowires patterned on Si substrate and investigated the field emission properties of the nanowires. Firstly, Au catalyst layers were fabricated on Si substrate by photo-lithography and lift-off process. The diameter of Au pattern was $50\;{\mu}m$ and the pattern was arrayed as $4{\times}4$. ZnO nanowires were grown on the Au catalyst pattern by the aid of Au liquid phase. The orientation of the ZnO nanowires was vertical on the whole. Sufficient brightness was obtained when the electric field was $5.4\;V/{\mu}m$ and the emission current was $5\;mA/cm^2$. The threshold electric field was $5.4\;V/{\mu}m$ in the $4{\times}4$ array of ZnO nanowires, which is quite lower than that of the nanowires grown on the flat Si substrate. The lower threshold electric field of the patterned ZnO nanowires could be attributed to their vertical orientation of the ZnO nanowires.