• 전기학회논문지
• /
• 제58권3호
• /
• pp.455-461
• /
• 2009

This paper proposes Direct Load Control(DLC) operation scheme using a bidding system and the methodology to value proper quantity decided by the DLC program, which is a kind of resources for stabilization of electricity market price during peak times by managing consumer electricity demand. Since DLC program in Korea is based on the contract with the customers participating in this program, it is difficult to anticipate voluntary participation. That is, incentive for participants in DLC program is insufficient. To cope with this point, it is necessary to develop a new market mechanism and market compatible operation scheme for DLC programs. DLC market mechanism is deemed to be equipped with iterative bidding system, independent operation from energy market, and interactive with bidding information on energy market. With this market mechanism, it is important to find the optimal operation point of DLC allowing for the factors of stabilizing the electricity market price and compensating DLC implementation. This paper focuses on the mathematical approaches for the bid-based DLC operation scheme and examines several scenarios for the following technical justifications: 1) stabilization of electricity market price during peak times, 2) elasticity of demand.

• 한국안전학회지
• /
• 제29권5호
• /
• pp.1-6
• /
• 2014

When the fluid energy convert into kinetic energy due to water hammer, the propagation velocity of pressure wave appear. The propagation velocity of pressure wave(1050 m/s) of very fast could be damage to the pipeline system. If the occurrence of water hammer is due to down-pressure, the faster the air exhaust or supply device is needed. it is high Speed Air Valve. In this paper, Each 3.12, 3.13, 3.72, $3.74kg/cm^2$ pipeline pressure were setting, and then executed pressure rapid drop for obtaining a high Speed Air Valve Operating time and pressure change data. the result was that pipe line pressure stabilization time were each 0.98, 1, 1.22, 1.25 sec. In other words, that pressure drop experimental results pipe line pressure was equal to atmospheric pressure without negative pressure After about one second. The study result would be useful to pipe line system stability design because this data could be foresee pressure stabilization time.

• 한국수소및신에너지학회논문집
• /
• 제29권4호
• /
• pp.370-377
• /
• 2018

Ball valve has been widely used in the field of high-pressure gas pipeline as an important component because of its low flow resistance and good leakage performance. The present paper focuses on the flow nature at the downstream of the ball valve used for gas pipelines according to valve opening rates. Steady 3-D RANS equations, SC/Tetra, have been introduced to analyze the flow characteristics inside the ball valve. Numerical boundary conditions at the inlet and outlet of the valve system are imposed by mass flow-rate and pressure, respectively. Velocity distributions obtained by numerical simulation are compared with respect to the valve opening rates of 30, 50, and 70%. Cavity distributions, asymmetry flow velocity and the flow stabilization point at each opening rate are also compared. When the valve opening rates are 30 and 50%, the flow stabilization requires the sufficient length of 10D or more due to the influence of the recirculation flow at the downstream of the valve.

• Corrosion Science and Technology
• /
• 제11권5호
• /
• pp.196-204
• /
• 2012

Corrosion failure of petrochemical facilities is one of the difficulties in maintenance, since operating conditions of crude oil production, storage, and refinement are very aggressive. UNS N08810, which has been used for crude oil transportation pipes and storage tanks in petrochemical industries, shows good resistance to general corrosion and localized corrosion in several environments. Among its environments, UNS N08810 showed better corrosion resistance in fuel gas containing sulfuric acid and phosphoric acid and sulfur. However, ductility and toughness at high temperature over about $500^{\circ}C$ were greatly reduced due to microstructural change. In general, welding process is the representative method to join the parts in industrial components. Because the alloy by welding can be sensitized and corroded, the manufacturing process should be controlled. In this work, UNS N08810 was used and heat treatment conditions including solution and stabilization treatments were controlled. Oxalic acid etch test by ASTM A262 Practice A was done to evaluate the qualitative sensitization in room temperature. Huey test by ASTM A262 Practice C was done to evaluate the intergranular corrosion rate in boiling 65% $HNO_3$ solution. Also, the microstructure by thermal history was analyzed. Experimental alloy showed high intergranular corrosion rate and its corrosion mechanism was elucidated.

• 한국세라믹학회지
• /
• 제34권10호
• /
• pp.1074-1082
• /
• 1997

Microstructure and permeability as a function of sintering temperature and composition were studied on the Ni$\delta$Cu0.4-$\delta$Zn0.6Fe2O4 ($\delta$=0, 0.1, 0.2, 0.3, 0.4) which was prepared by Cu2+ substitution for Ni2+ in Ni.0.4Zn0.6Fe2O4, then followed by 8 wt% CuO and 1wt% Bi2O3 as sintering aids. It was found that NiCuZn ferrite in which Cu2+ is substituted for Ni2+ is more effective in reduction of sintering temperature than Ni.0.4Zn0.6Fe2O4, containing CuO as a sintering aid. The specimen $\delta$=0.2 sintered at 90$0^{\circ}C$ for 2hr exhibited the highest initial permeability value ($\mu$o=280 at 1Mhz), but the real permeability decreased at the frequency under 10 MHz. EPMA analysis showed that Ni$\delta$Cu0.4-$\delta$Zn0.6Fe2O4 ($\delta$=0.4), sintered at 95$0^{\circ}C$ for 2hrs consisted of three phase regions of Ni.0.3Cu0.1Zn0.6Fe2O4 region, Cu and Bi liquid existed at the 3-point boundary, although the stabilization energy of Ni2+ is higher than that of Cu2+ in B site.

• Corrosion Science and Technology
• /
• 제16권4호
• /
• pp.194-200
• /
• 2017

Stress-corrosion cracking (SCC) of alloy 600 and alloy 800 in 0.5 mol/L thiosulfate solution during constant strain was investigated using electrochemical noise (EN) combined with 3-D microscope techniques. The in-situ morphology observation and EN results indicate that the SCC process could be divided into three stages: (1) passive film stabilization and growth, (2) crack initiation, (3) and crack growth. Power Spectral Density (PSD) and the probability distribution obtained from EN were used as the "fingerprint" to distinguish the different processes. During passive film stabilization and growth, the current noise signals resembled "white noise": when the crack initiated, many transient peaks could be seen in the current noise and the wavelet energy at low frequency as well as the noise resistance decreased. After crack propagation, the noise amplitudes increased, particularly the white noises at low and high frequencies ($W_L$ and $W_H$) in the PSDs. Finally, the detection of metal structure corrosion in a simulated sea splash zone and pipeline corrosion in the atmosphere are established.

• Elastomers and Composites
• /
• 제54권4호
• /
• pp.335-344
• /
• 2019

In this work, styrene butadiene rubber (SBR) and styrene butadiene styrene (SBS) were used to modify asphalt, resulting in SBR- and SBS-modified asphalt, respectively. The two modified asphalts were emulsified with a nonionic emulsifier (Span 60) and cationic emulsifiers (ID, DDA) and their phase stabilization was investigated via particle size, Zeta potential, and flow behavior analysis. With increasing amount of the mixed emulsifier, the particle size decreased, leading to an increase in viscosity. The shear thinning behaviors and Zeta potential values ranging from 35-65 mV were determined and remained considerably stable. In addition, the adhesion strength and compression strength of the SBR-and SBS-modified asphalt emulsion were evaluated via surface free energy examination. The remarkable adhesion and compression strengths were estimated when 5 phr ID and 6 phr DDA were added to the emulsified asphalt modified with SBR and SBS. Therefore ID and DDA, the two cationic surfactants, played significant roles in improving the dispersion and interfacial adhesion strength, resulting in the improved adhesion and compression strength of the emulsified asphalts modified with SBR and SBS.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2002년도 추계학술대회 논문집
• /
• pp.119-123
• /
• 2002

Liquefied Natural Gas(LNG) continues to attract modern gas industries as well as domestic markets as their main energy source in the recent years. This is mainly because LNG is inherently cleaner and more energy efficiency than other fuels. Offshore LNG production plant is of interest to many oil producing companies all over the world. This article discuss about the production process encountered while developing such a production facility. Typical offshore oil and gas processing required for oil stabilization and other optional units that can be added to the facilities. The production process can broadly be divided into five major units namely, (i) Oil Stabilization unit, (ii) Gas Treatment unit, (iii) Methane Recovery unit, (iv) Distillation unit and (v) LNG Liquefaction unit. The process simulation was carried out for each unit with a given wellhead composition. The topside facilities of offshore LNG production plant will be very similar to the process adopted in offshore processing platform along with the typical onshore LNG production plant. However, the process design problems associated with FPSO motion to be taken care of while developing floating LNG production plant.

• 대한기계학회논문집
• /
• 제13권3호
• /
• pp.317-322
• /
• 1989

본 연구에서는 Liu의 매트릭스를 강소성 유한요소법에 도입하여 통상의 소성가공 공정중에 있는 피가공물의 3차원 변형을 실용적인 수준에서 해석 가능케 하는 강소성 유한요소법을 도입하여 통상의 소성가공 공정중에 있는 피가공물의 3차원 변형을 실용적인 수준에서 해석 가능케 하는 강소성 유한요소법을 제안하고 실례를 통하여 제안한수법에 의하여 얻어진 해의 안정성과 계산효율을 검토한다.

• Journal of Magnetics
• /
• 제21권2호
• /
• pp.266-272
• /
• 2016

Transcranial magnetic stimulation devices has been used mainly for diagnostic purposes by measuring the functions of the nervous system rather than for treatment purposes, and has a problem of considerable energy fluctuations per repeated pulse. The majority of strokes are caused by ischemia and result in brain tissue damage, leading to problems of the central nervous system including hemiparesis, dysfunction of language and consciousness, and dysfunction of perception. Control is difficult and the size is large due to the difficulty of digitalizing the energy stored in a capacitor, and there are many heavy devices. In addition, there are many constraints when it is used for a range of purposes such as head and neck diagnosis, treatment and rehabilitation of nerve palsy, muscle strengthening, treatment of urinary incontinence etc. Output stabilization and minimization of the energy variation rate are required as the level of the transcranial magnetic stimulation device is dramatically improved and the demand for therapeutic purposes increases. This study developed a compact, low cost transcranial magnetic stimulation device with minimal energy variation of a high repeated pulse and output stabilization using a real time capacitor charge discharge voltage. Ischemia was induced in male SD rats by closing off the common carotid artery for 5 minutes, after which the blood was re-perfused. In the cerebrum, the number of PARP reactive cells after 24 hours significantly decreased (p < 0.05) in the TMS group compared to the GI group. As a result, TMS showed the greatest effect on necrosis-related PARP immuno-reactive cells 24 hours after ischemia, indicating necrosis inhibition, blocking of neural cell death, and protection of neural cells.