• The Journal of Korean Academy of Prosthodontics
• /
• v.38 no.3
• /
• pp.360-365
• /
• 2000

The completely edentulous patient has few treatment options in conventional dentistry. When implants are considered, treatment plans range from a 2-implant overdenture to a completely implant-supported prosthesis. Fixed prosthesis is often the preferred selection of the edentulous patient. fixed full-arch cert amo-metal restorations can be a predictable implant treatment modality for the edentulous patient. Implant-supported fixed prosthesis has several advantages: predictability, fixedness, retrievability, improved function, lower maintenance of prosthesis, long-term published success. Edentulous patients with a severely resorbed mandible often experience problems with their dentures. Treatment concepts involving two to four implants for the support of an overdenture have been proposed. There seems to be no need to insert more than two endosteal implants to support an overdenture, however, long-term prospective studies are needed to support this notion. Using short endosseous implants and an overdenture in the extremely resorbed mandible is a justified treatment option because of the relative simplicity and low morbidity of this treatment strategy. Implant-supported overdenture has several advantages: Cost, retrievability, hygiene access, profile and contour control, increased retention and stability, implant installed in a predicted region(ant. mandible).

• Journal of Mechanical Science and Technology
• /
• v.14 no.8
• /
• pp.867-878
• /
• 2000

In order to study unsteady aerodynamic loads on high speed trains passing by each other 350km/h, three-dimensional flow fields around trains during the crossing event are numerically simulated using three-dimensional Euler equations. Roe's FDS with MUSCL interpolation is employed to simulate wave phenomena. An efficient moving grid system based on domain decomposition techniques is developed to analyze the unsteady flow field induced by the restricted motion of a train on a rail. Numerical simulations of the trains passing by on the double-track are carried out to study the effect of the train nose-shape, length and the existence of a tunnel on the crossing event. Unsteady aerodynamic loads-a side force and a drag force-acting on the train during the crossing are numerically predicted and analyzed. The side force mainly depends on the nose-shape, and the drag force depends on tunnel existence. Also. a push-pull (i.e.impluse force) force successively acts on each car and acts in different directions between the neighborhood cars. The maximum change of the impulsive force reaches about 3 tons. These aerodynamic force data are absolutely necessary to evaluate the stability of high speed multi-car trains. The results also indicate the effectiveness of the present numerical method for simulating the unsteady flow fields induced by bodies in relative motion.

• Journal of Environmental Impact Assessment
• /
• v.2 no.2
• /
• pp.59-71
• /
• 1993

Evaluation methods are employed in environmental impact assessment to choose between different project site, to determine the required measures to compensate impact and to decide whether the environmental impacts are more important than the social or economic effects of a project. The main obstacles that restrict use of quantitative evaluation method are a Lack of knowledge about the environmental effects (e.g. if impacts on wildlife or landscape amenities are predicted) and the relative importance of economic and social issues compared with nature conservation stability of ecosystem or landscape beauty. In Germany, the most common method for site planning is the "ecological risk analysis". It is a kind of multi-criteria-decision-method based on quantitative and qualitative description and ordinal ranking. The various kinds of "ecological balancing methods" that are more recently developed (within the last decade) to quantify the required amount for compensatory measures instead often use cardinal figures to express the value of ecosystems, the intensity of impacts, the need for additional measures to compensate for long recuperative periods when restoring ecosystems and so on. There are still only a view attempts to quantify decisions between environmental and socio-economic issues. Multicriteria-analysis as well as cost-benifit-analysis was used. Some new approaches which are still in a preliminary status are based on contingent valuation and on calculations for compensatory payments (instead of compensatory measures).

• Tribology and Lubricants
• /
• v.26 no.4
• /
• pp.246-253
• /
• 2010

Friction characteristics of the brake friction materials without environmentally regulated ingredients were examined to find their role in the brake performance. Five friction materials were produced based on a nearcommercial formulation by changing the relative amount of potentially hazardous ingredients to health and environment, such as $Sb_2S_3$, potassium titanate, and brass fiber. Tribological properties of the friction materials were obtained using a scale dynamometer and Krauss type tribometer. Results showed that the excluded three ingredients played important synergetic effects on tribological properties in terms of fade resistance, wear resistance and friction effectiveness. In particular, brass fibers played important roles in the friction stability by providing excellent thermal diffusivity at the friction interface. Potassium titanate whiskers showed excellent fade resistance and wear resistance compared to the substituted barite. Antimony trisulfide, on the other hand, showed little effect on the high temperature fade resistance and wear resistance, while it increased friction effectiveness at moderate temperatures. The friction materials without the three ingredients showed severe fade, indicating antisynergy effects.

• Korean journal of food and cookery science
• /
• v.9 no.4
• /
• pp.298-302
• /
• 1993

The Crude ginerol from ginger was collected to investigate the possibility of application to food products as a natural antioxidant. The antioxidant activity of gingerols according to fatty acid composi-tion of several oils, were examined by measuring peroxide value(POV). The induction period(If) of fish oil, sdybean oil, lard and palm oil was 5.0, 17.0, 38.4 and 57.6 hours respectively by measuring POV during storge at $85^{\circ}C$. The relative antioxidant effectiveness(RAE) of gingerol group was lard ; 219, soybean oil; 176, fish oil; 160 and palm oil; 146%, while the RAE of'BHT group was lard; 238, palm oil; 158, soybfan oil; 132 and fish oil; 122%.

• Proceedings of the Safety Management and Science Conference
• /
• 2005.11a
• /
• pp.537-557
• /
• 2005

The estimate on volatility of stock price is related with optimum of portfolio and Important for allocation of capital asset. If the volatility of stock price is varied according to macroeconomic variables on monetary policy and industrial production, it will assist capital asset to allocate. This paper is related with stock market volatilities on macroeconomic variables in U.S. and Europe, Korea. And, it Is pertain to vary in time of this variables. Thus, this paper is related with volatilities of monetary and physical macroeconomic variables on basis of statistics. And, it is ranged front capital investment to portfolio allocation. Also, this paper takes out of sample forecast and study more after this. In case Germany, France, Italy and the Netherlands, the relative importance of monetary policy and Industrial production Is different from these countries. In case Italy and the Netherlands, monetary policy is primary factor at stabilizing for volatility of stock price. In case Korea, increasing monetary policy and industrial production is positively affected stock market. It is that the positive effect of stock price is caused by mollifying monetary policy and economic growth. Specially, this conclusion is similar to US. In Korea, gradual increase in monetary and industrial production is necessary to stability of stock market. It is different to previous results on basis of increasing stock price of money in long period.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.6
• /
• pp.1245-1254
• /
• 2011

This paper proposes a target tracking algorithm for wheeled mobile robots using in various fields. For the stable tracking, we apply a vision system to a mobile robot which can extract targets through image processing algorithms. Furthermore, this paper presents an algorithm to position the mobile robot at the desired location from the target by estimating its relative position and attitude. We show the problem in the tracking method using the Position-Based Visual Servo(PBVS) control, and propose a tracking method, which can achieve the stable tracking performance by combining the PBVS control with Image-Based Visual Servo(IBVS) control. When the target is located around the outskirt of the camera image, the target can disappear from the field of view. Thus the proposed algorithm combines the control inputs with of the hyperbolic form the switching function to solve this problem. Through both simulations and experiments for the mobile robot we have confirmed that the proposed visual servo control method is able to enhance the stability compared to of the method using only either PBVS or IBVS control method.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1375-1386
• /
• 2016

To decouple the secondary saliencies in sensorless permanent magnet synchronous machine (PMSM) drives, a repetitive control (RC) in the angle domain is proposed. In this paper, the inductance model of a concentrated windings surface-mounted PMSM (cwSPMSM) with strong secondary saliencies is developed. Due to the secondary saliencies, the estimated position contains harmonic disturbances that are periodic relative to the angular position. Through a transformation from the time domain to the angle domain, these varying frequency disturbances can be treated as constant periodic disturbances. The proposed angle-domain RC is plugged into an existing phase-locked loop (PLL) and utilizes the error of the PLL to generate signals to suppress these periodic disturbances. A stability analysis and parameter design guidelines of the RC are addressed in detail. Finally, the proposed method is carried out on a cwSPMSM drive test-bench. The effectiveness and accuracy are verified by experimental results.

• Proceedings of the KIEE Conference
• /
• 2009.07a
• /
• pp.1236_1237
• /
• 2009

Organic light emitting diode (OLED) is currently the focus of intense interest in the field of photonics. It is attractive for the in low-operating voltage, low power consumption, easy fabrication and low cost. A typical OLED consists of one or more organic layers sandwiched between a high work function anode, such as indium tin oxide (ITO), and a low work function cathode such as Ca, Mg:Ag, and Al. Tris-(8-hydroxy)quinolinealuminum ($Alq_3$) has taken a prominent position in the development of OLED due to its relative stability as an electron transporting and emitting material. We investigated an efficiency improvement of the OLED depending on thickness variation of $Alq_3$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.133-133
• /
• 2013

For both oxygen reduction (ORR) and hydrogen oxidation reactions (HOR) of proton electrolyte membrane fuel cells (PEMFCs), alloying Pt with another transition metal usually results in a higher activity relative to pure Pt, mainly due to electronic modification of Pt and bifunctional behaviour of alloy surface for ORR and HOR, respectively. However, activity and stability are closely related to the preparation of alloy nanoparticles. Preparation conditions of alloy nanoparticles have strong influence on surface composition, oxidation state, nanoparticle size, shape, and contamination, which result from a large difference in redox priority of metal precursors, intrinsic properties of metals, increasedreactivity of nanocrystallites, and interactions with constituents for the synthesis such as solvent, stabilizer, and reducing agent, etc. Carbon-supported Pt-Ni alloy nanoparticles were prepared by the borohydride reduction method in anhydrous solvent. Pt-Ru alloy nanoparticles supported on carbon black were also prepared by the similar synthetic method to that of Pt-Ni. Since electrocatalytic reactions are strongly dependent on the surface structure of metal catalysts, the atom-leveled design of the surface structure plays a significant role in a high catalytic activity and the utilization of electrocatalysts. Therefore, surface-modified electrocatalysts have attracted much attention due to their unique structure and new electronic and electrocatalytic properties. The carbon-supported Au and Pd nanoparticles were adapted as the substrate and the successive reduction process was used for depositing Pt and PtM (M=Ru, Pd, and Rh) bimetallic elements on the surface of Au and Pd nanoparticles. Distinct features of the overlayers for electrocatalytic activities including methanol oxidation, formic acid oxidation, and oxygen reduction were investigated.