• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.34 no.7
• /
• pp.289-296
• /
• 1985

The Townsend primary ionization coefficient a was measured by the luminous-flux method using the fact that the intensity of radiant light is proportional to electron density in the townsend discharge domain. The ranges of measurements were 15for He gas and 10

• Bulletin of the Korean Chemical Society
• /
• v.11 no.3
• /
• pp.214-220
• /
• 1990

We have studied the Infrared Multiphoton Dissociation (IRMPD) of 1-bromo-3-chloropropane by using the pulsed $CO_2$ laser. The product yields and the HCl/HBr branching ratios in IRMPD of $BrCH_2CH_2CH_2Cl$ are studied under the focused beam geometry as a function of buffer gas (He) pressure, laser energy, and photolysing wavelength. It is observed that the total dissociation yield has a laser energy dependence of 1.8-2.0 power order and the branching ratio is very slightly dependent on the pulse energy for the laser lines employed. The dependences of total dissociation yield and branching ratio on the buffer gas pressures show that the dissociation yield monotonically decreases and the branching ratio slightly decreases with the increase of the buffer gas pressure. The Energy-Grained Master Equation (EGME) was applied to explain the laser pulse energy and the buffer gas pressure(He) dependence of the dissociation yield and the branching ratio.

• Journal of Welding and Joining
• /
• v.31 no.3
• /
• pp.60-65
• /
• 2013

Ar, $N_2$, and He are the conventional kind of shield gas that are used for laser welding. Many researches on the impact of laser welding shield gas have been done, and it is on going until now. However, there are few studies that analyze the changes and differences of the plasma emission signal. Therefore, in this study, we evaluated the change in the penetration characteristics according to the type of shield gas during fiber laser welding impacts to the plasma signal. As a result, if was checked that the difference in molecular weight of Ar, $N_2$, and He affects to the amount of spatter, and also found that the measured plasma radiation signal changes similar to the order of the molecular weight of the gases. Especially, clear change on the signal intensity per each shield gas was measured through RMS, and found that the shield gas was nothing to do with the FFT analyzed result.

• Journal of the Korean Vacuum Society
• /
• v.15 no.1
• /
• pp.73-80
• /
• 2006

Thermally-driven effusion of inert gases out from Si(100), into which energetic $\~l keV\;He^+,\;Ne^+,\;A^r+,\;and\;Kr^+ ions$ had been implanted at a moderate substrate temperatures of $\~400 K$, was investigated by means of temperature-programmed desorption (TPD) mass spectrometry. While He effused out broadly over $500\~1,100 K$, Ne, Ar, and Kr effusion occurred sharply at 810, 860, and 875 K, respectively. Hydrogen adsorption/desorption analysis for the ion-treated Si(100) surfaces indicated minimal to severe damage by ions with increasing mass from He to Kr. Implications of these results in light of literature reports are discussed.

• Journal of the Korean Vacuum Society
• /
• v.20 no.6
• /
• pp.409-415
• /
• 2011

The method to improve the detection sensitivity of Hand-held XRF (X-Ray Fluorescence) device currently being developed is discussed. To minimize the loss of the intensity due to atmospheric gas molecules, the vacuum module, which can be filled with atmospheric or He gas, between the sample and the detector was installed. And the change of the detection sensitivity was measured in a vacuum and in the He gas-filled state. As a result, the following three important results were obtained; Firstly, XRF intensity was increased 2~4 times in the low energy range (3~4 keV). It is a very important result because the enhancement of the detection sensitivity means shortening of the detection time in Hand-held XRF device. Secondly, the possibility of detection of the elements less than 3 keV in emission energy was confirmed. Thirdly, the absorption by atmospheric gas molecules can be minimized without vacuum- sealed vessel in Hand-held XRF device, if the vacuum module filled with He gas is used. We concluded that all of three results are very meaningful in the development of a Hand-held XRF device.

• Journal of Radiation Protection and Research
• /
• v.22 no.2
• /
• pp.119-125
• /
• 1997

PHWR achieves high neutron economy by adopting heavy water as its moderator and coolant. On the other hand it permits much tritium generation, compared to LWR, due to the neutron capture reaction of deuterium in heavy water. Meanwhile in the reactor core, $^3He formed as the result of-decay of tritium, captures a thermal neutron and transforms to tritium again. The existing calculation models on tritium generation in PHWR neglect the contribution of $^3He$ in both moderator and coolant due to its relatively low solubility. However the neutron capture cross-section of $^3He$ is almost $1.6{\times}10^7$ times as large as that of deuterium. That means that the dissolved amount of 0.03 ppm of $^3He$ in heavy water is enough to generate the same amount of tritium as that generated by the deuterium of total heavy water in the system. This study dealt with the contribution of $^3He$ to tritium generation. As a sample case, the contribution of $^3He$ to the tritium generation in Wolsong #1 was evaluated and compared to the measured values. According to the result of this study, it is concluded that $^3He$ in coolant contributes very much to the tritium generation but that in moderator shows negligible effects due to the low solubility and $^4He$ cover gas. At the beginning of the plant operation, the contribution of $^3He$ is slightly greater than the measured value but agrees well with the measured as the operating time increases.

• Journal of Information Display
• /
• v.10 no.4
• /
• pp.195-201
• /
• 2009

The temporal dark- and bright-image sticking phenomena were examined relative to the He contents under 11% Xe content in the 50-in HD and FHD AC-PDPs with a ternary gas mixture (Xe-He-Ne). To compare the temporal dark- and bright-image sticking phenomena under various He contents, the differences in the disappearing time, display luminance, perceived luminance, infrared emission, color coordinate, color temperature, and discharge current before and after discharge were measured under 0, 35, 50, and 70% He contents. It was found that temporal dark- and bright-image sticking were reduced in proportion to the increase in He %. Thus, a high He content contributes to the reduction of temporal dark- and bright-image sticking.

• Ocean Science Journal
• /
• v.43 no.1
• /
• pp.17-24
• /
• 2008

Over a period of 5 days between August 12 and 17, 2005, we performed a gas exchange experiment using the dual tracer method in a tidal coastal ocean located off the southern coast of Korea. The gas exchange rate was determined from temporal changes in the ratio of $^3He$ to $SF_6$ measured daily in the surface mixed layer. The measured gas exchange rate($k_{CO_2}$), normalized to a Schmidt number of 600 for $CO_2$ in fresh water at $20^{\circ}C$, was approximately $5.0\;cm\;h^{-1}$ at a mean wind speed of $3.9\;ms^{-1}$ during the study period. This value is significantly less than those obtained from floating chamber-based experiments performed previously in estuarine environments, but is similar in magnitude to values obtained using the dual tracer method in river and tidal coastal waters and values predicted on the basis of the relationship between the gas exchange rate and wind speed (Wanninkhof 1992), which is generally applicable to the open ocean. Our result is also consistent with the relationship of Raymond and Cole (2001), which was derived from experiments carried out in estuarine environments using $^{222}Rn$ and chlorofluorocarbons along with measurements undertaken in the Hudson River, Canada, using $SF_6$ and $^3He$. Our results indicate that tidal action in a microtidal region did not discernibly enhance the measured $k_{CO_2}$ value.

• Proceedings of the Korean Institute of Surface Engineering Conference
• /
• 2012.11a
• /
• pp.35-50
• /
• 2012

$900^{\circ}C$이상 초고온 He-gas 분위기 또는 용융불화염 (molten salts, FLINAK) 환경에서 사용될 VHTR(Very High Temperature Reactor)의 IHX(Intermediate heat exchanger)용 열수송 구조재료로 가장 가능성이 높은 합금인 Inconel 617 및 Hastelloy X 상에 습식화학적, 물리적기상합성법(Vacuum arc-plasma과 RF magnetron sputtering) 및 pack cementation에 의한 표면개질 및 마이크로 초내열(refractory ceramics) 코팅층(TiN, TiCN, TiAlN, $Al_2O_3$, $TiO_2$)을 형성시켰다. 고온 장기사용 시 문제가 될 수 있는 고온에서의 조직변화, 미세구조와 상(phase)형성, 고온 부식 및 그에 따른 마모(wear resistance) 손상 등 이들 소재의 내열, 내식 및 내마모 물성을 개선하는 연구를 수행하였다. TiAlN 박막의 경우 공기분위기에서 N이 분해되나 치밀한 산화물($TiO_2/Al_2O_3$ layer)을 형성하여 내식성 있는 보호피막을 형성함으로 기판과의 열팽창 계수로 인한 박리가 발생하지 않아 보호피막으로 적합하였다. Pack cementation법에 의한 aluminiding(Al-Ni합금)도 He 및 공기분위기에서 고온물성의 저하를 가져오는 $Cr_2O_3$의 생성을 충분히 억제하고 있었으며 He 및 air 분위기에서 사용이 가능한 박막으로 여겨진다. 내열 및 내식성에 대한 실험을 종합한 결과, 공기분위기에서 사용할 수 없는 박막은 He-gas 및 FLINAK(LiF-NaF-KF) 용융염 분위기에서도 사용할 수 없었으며, He-gas, FLINAK 및 air 분위기에서 모두 사용이 가능한 박막으로는 Inconel 617에서는 $(TiO_2-)Al_2O_3$, TiAlN 및 Al-Ni이었고 Hastelloy에서는 Al-Ni 및 $Al_2O_3$가 가장 적당하였다.

• Journal of Welding and Joining
• /
• v.23 no.1
• /
• pp.41-47
• /
• 2005

Arc pressure is one of important factors in understanding physical arc phenomena. Especially it affects on the penetration, size and shape of TIG welding. Some researches were reported on the effect of arc pressure in low and middle current region. But there are not any research in high current region. The purpose of this study is to investigate the arc pressure distribution with mixing ratio of shield gas such as Ar and He gases. A Cu block with water cooling was specifically designed and used as an anode electrode in order to measure the arc pressure in high current region. Then, the arc pressure distribution was measured with change in welding current and mixing ratio of shield gases. The arc force was obtained by numerically integrating the measured results. As the results, it was shown that the arc pressure was concentrated at the central part of the arc in middle and high current regions when a pure Ar gas was used. In case of Ar + He mixing gas, the arc pressure was much lower than that of pure Ar gas. In addition, it was widely distributed to radial direction.