• Corrosion Science and Technology
• /
• v.19 no.2
• /
• pp.89-99
• /
• 2020

The inhibition of pitting corrosion failure of copper sprinkler tubes in wet sprinkler systems was studied. First, an apparatus and technology for removing air in the sprinkler tubes by vacuum pumping and then filling the tubes with water were developed. Using this apparatus and technology, three methods for inhibiting the pitting corrosion of the copper sprinkler tubes installed in several apartment complexes were tested. The first one was filling the sprinkler tubes with water bubbled by high-pressure nitrogen gas to reduce the dissolved oxygen concentration to lower than 2 ppm. In the second method, the dissolved oxygen concentration of water was further reduced to lower than 0.01 ppm by sodium sulfite. In the third method, the sprinkler tubes were filled with benzotriazole (BTAH) dissolved in water. The third method was the most effective, reducing the failure frequency of the sprinkler tubes due to pitting corrosion by more than 80%. X-ray photoelectron spectroscopy analyses confirmed that a Cu-BTA layer was well coated on the inside surface of the corrosion pit, protecting it from corrosion. A potentiodynamic polarization test showed that BTAH should be very effective in reducing the corrosion rate of copper in the acidic environment of the corrosion pit.

• Nuclear Engineering and Technology
• /
• v.37 no.3
• /
• pp.279-286
• /
• 2005

A prototype of a relativistic proton generation system, based on laser-induced plasma interaction, has been designed and fabricated. The system is composed of three major parts: a fs TW laser; a target chamber, including targets and controls; and a diagnostic system for charged particles and lasers. An Offner-type pulse stretcher for chirped pulse amplification (CPA) and eight pass pre-amplifier are installed. The main amplifier will be integrated with a new pumping laser. The design values of the laser at the first stage are 1 TW in power and 50 fs in pulse duration. We expect to generate protons with their maximum energy of approximately 3 MeV and the flux of at least $10^6$ per pulse using a 10 $\mu$m Al target. A prototype target chamber with eight 8-inch flanges, including target mounts, has been designed and fabricated. For laser diagnostics, an adaptive optics based on the Shack-Hartmann type, beam monitoring, and alignment system are all under development. For a charged particle, CR-39 detectors, a Thomson parabola spectrometer, and Si charged-particle detectors will be used for the density profile and energy spectrum. In this paper, we present the preliminary design for laser-induced proton generation. We also present plans for future work, as well as theoretical simulations.

• Journal of Advanced Marine Engineering and Technology
• /
• v.10 no.1
• /
• pp.74-84
• /
• 1986

Ejectors, having no moving, lubricating and leaking parats, are widely used as marine pumps because of its high working confidence. For instance, uses in ships are stripping in crude oil tank, bilge discharge in engine room, ballast water pumping on are carrier, and brine discharge from fresh water generator. And it is also used as cooling water recirculating pump in boiling water type nuclear reactor and deep-well pump. It is not easy to determine the optimal dimension for designing each ejector agreed with its suggested performance condition, because complicated calculations must be repeated to obtain the maximum efficiency affected by flowrate ratio, head ratio, area ratio and so on. Therefore, it is considered that the CAD (Computer-Aided Design) for ejector is a powerful method for design according to the individual design condition. In this paper, a computer program for water ejector design is developed based on the previous paper on theoretical analysis and experimental results for water ejector. And from the theoretical approach, an equation for the working limit and an equation for determing the shape of throat are obtained. The validity of the present computer program is sufficiently confirmed through the comparison of the computed results with the main dimension of the previous manufactured water ejector. This program will be easily developed as the CAD for various kinds of ejectors, including steam ejector.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.308-327
• /
• 2004

As use of tunnels and subways increase there also are accidents proportionate to it. Daegu Subway Station fire, Hongjimoon tunnel fire led people to be conscious of disaster protection and as a result, there is a trend to adopt standards for fire protection. Accordingly, this thesis is focused on investigating various fire and water protection related issues for subaqueous tunnel under Ran river. The thesis developed evacuation and disaster prevention plan as fire level increases and have identified the suitability of disaster prevention through evacuation and fire simulation, countermeasure of a water leakage during construction and operation considering the subaqueous tunnel. And we selected EPB shield TBM equipment considering the ground condition and effect of boring hole, and accomplished reasonable water protection design through setting goals using event-tree method, as well as examining model test of boring hole and flooding in heavy rain. Also included structured total system consist of water leakage sensing system, water protection gate, pumping system and fire protection system to respond systematically in emergency.

• ETRI Journal
• /
• v.37 no.6
• /
• pp.1188-1198
• /
• 2015

In this paper, a multi-time programmable (MTP) cell based on a $0.18{\mu}m$ bipolar-CMOS-DMOS backbone process that can be written into by using dual pumping voltages - VPP (boosted voltage) and VNN (negative voltage) - is used to design MTP memories without high voltage devices. The used MTP cell consists of a control gate (CG) capacitor, a TG_SENSE transistor, and a select transistor. To reduce the MTP cell size, the tunnel gate (TG) oxide and sense transistor are merged into a single TG_SENSE transistor; only two p-wells are used - one for the TG_SENSE and sense transistors and the other for the CG capacitor; moreover, only one deep n-well is used for the 256-bit MTP cell array. In addition, a three-stage voltage level translator, a VNN charge pump, and a VNN precharge circuit are newly proposed to secure the reliability of 5 V devices. Also, a dual memory structure, which is separated into a designer memory area of $1row{\times}64columns$ and a user memory area of $3rows{\times}64columns$, is newly proposed in this paper.

• Bulletin of the Korean Chemical Society
• /
• v.31 no.4
• /
• pp.989-998
• /
• 2010

The titled dye of DBPI gives amplified spontaneous emission (ASE) with maximum at 580 nm upon pumping by nitrogen laser (${\lambda}_{ex}\;=\;337.1\;nm$). The ground state absorption cross section (${\sigma}_A$) and emission cross section (${\sigma}_E$) as well as effective emission cross section(${\sigma}^*_E$) have been determined. The electronic absorption spectra of DBPI were measured in ethanol and tetrahydrofuran at room and low temperature. DBPI displays molecular aggregation in water. The photochemical reactivity of DBPI was also studied in carbon tetrachloride upon irradiation with 525 nm light. The electrochemical investigation of DBPI dye has been carried out using cyclic voltammetry and convolution deconvolution voltammetry combined with digital simulation technique at a platinum electrode in 0.1 mol/L tetrabutyl ammonium perchlorate (TBAP) in two different solvents acetonitrile ($CH_3CN$) and dimethylformamide (DMF). The species were reduced via consumption of two sequential electrons to form radical anion and dianion (EE mechanism). In switching the potential to positive direction, the compound was oxidized by loss of two sequential electrons, which were followed by a fast dimerization and/or aggregation process i.e $EC_{dim1}EC_{dim2}$ mechanism. The electrode reaction pathway and the chemical and electrochemical parameters of the investigated compound were determined using cyclic and convolutive voltammetry. The extracted electrochemical parameters were verified and confirmed via digital simulation method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.2
• /
• pp.183-189
• /
• 2012

Most of the domestic residential buildings have used the traditional radiant heating system, circulating hot water through the cross-linked polyethylene(PE-X) pipe buried in the floor panel of the heating space. New type of the heating panel was recently developed using heat pipes with double wicks. Some experiments were carried out in this study to verify the thermal characteristics of this heating system at the unit heating space which surrounded by outer space whose temperature of air be maintained scheduled value with time. Through the various experiments with several parameters, such as flow rate, inlet and outlet temperatures of hot water and the heating duration and so on, we found that the floor heating system with heat pipes was able to reduce the pumping power for hot water circulation by 4~31% compared with the conventional panel heating system using PE-X pipe. These results could be used for optimal design and efficient operation of the heating system as well as improvement of thermal comfort.

• Nuclear Engineering and Technology
• /
• v.49 no.1
• /
• pp.82-91
• /
• 2017

Liquid alloy systems have a high degree of thermal conductivity, far superior to ordinary nonmetallic liquids and inherent high densities and electrical conductivities. This results in the use of these materials for specific heat conducting and dissipation applications for the nuclear and space sectors. Uniquely, they can be used to conduct heat and electricity between nonmetallic and metallic surfaces. The motion of liquid metals in strong magnetic fields generally induces electric currents, which, while interacting with the magnetic field, produce electromagnetic forces. Electromagnetic pumps exploit the fact that liquid metals are conducting fluids capable of carrying currents, which is a source of electromagnetic fields useful for pumping and diagnostics. The coupling between the electromagnetics and thermo-fluid mechanical phenomena and the determination of its geometry and electrical configuration, gives rise to complex engineering magnetohydrodynamics problems. The development of tools to model, characterize, design, and build liquid metal thermomagnetic systems for space, nuclear, and industrial applications are of primordial importance and represent a cross-cutting technology that can provide unique design and development capabilities as well as a better understanding of the physics behind the magneto-hydrodynamics of liquid metals. First studies for the development of computational tools for the design of liquid metal electromagnetic pumps are discussed.

• International Journal of Fluid Machinery and Systems
• /
• v.3 no.4
• /
• pp.352-359
• /
• 2010

In recent years, the market has shown increasing interest in pump-turbines. The prompt availability of pumped storage plants and the benefits to the power system achieved by peak lopping, providing reserve capacity, and rapid response in frequency control are providing a growing advantage. In this context, there is a need to develop pumpturbines that can reliably withstand dynamic operation modes, fast changes of discharge rate by adjusting the variable diffuser vanes, as well as fast changes from pumping to turbine operation. In the first part of the present study, various flow patterns linked to operation of a pump-turbine system are discussed. In this context, pump and turbine modes are presented separately and different load cases are shown in each operating mode. In order to create modern, competitive pump-turbine designs, this study further explains what design challenges should be considered in defining the geometry of a pump-turbine impeller. The second part of the paper describes an innovative, staggered approach to impeller development, applied to a low head pump-turbine project. The first level of the process consists of optimization strategies based on evolutionary algorithms together with 3D in-viscid flow analysis. In the next stage, the hydraulic behavior of both pump mode and turbine mode is evaluated by solving the full 3D Navier-Stokes equations in combination with a robust turbulence model. Finally, the progress in hydraulic design is demonstrated by model test results that show a significant improvement in hydraulic performance compared to an existing reference design.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1994.05a
• /
• pp.116-119
• /
• 1994

The characteristics of the Si-SiO$_2$ interface and the degradation in the short channel(L${\times}$W=1.7$\mu\textrm{m}$${\times}$15$\mu\textrm{m}$) SONOSFET nonvolatile memory devices, fabricated on the basis of the existing n-well CMOS processing technology for 1 Mbit DRAM with the 1.2$\mu\textrm{m}$ m design rule, were investigated using the charge pumping method. The SONOSFET memories have the tripple insulated-gate consisting of 30${\AA}$ tunneling oxide 205${\AA}$ nitride and 65${\AA}$ blocking oxide, The acceleration method which square voltage pulses of t$\_$p/=10msec, Vw=+19V and V$\_$E/=-22V continue to be alternatly applied to gale, was used to investigate the degradation of SONOSFET memories with the write/erase cycle. The degradation characteristics were ascertained by observing the change in the energy and spatial distributions of the interface trap density.