• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1199-1210
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• 2017

A new in-line method for sampling neutrons emitted in (${\alpha}$,n) reactions based on alpha particle source information has been developed for continuous-energy Monte Carlo simulations. The new method uses a continuous-slowing-down model coupled with (${\alpha}$,n) cross section data to precompute the expected neutron yield over the alpha particle lifetime. This eliminates the complexity and computational cost associated with explicit charged particle transport. When combined with an integrated alpha particle decay source sampling capability, the proposed method provides an efficient and accurate method for sampling (${\alpha}$,n) neutrons based solely on nuclide inventories in the problem, with no additional user input required. Results from several example calculations show that the proposed method reproduces the (${\alpha}$,n) neutron yields and energy spectra from reference experiments and calculations.

• Nuclear Medicine and Molecular Imaging
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• 제41권1호
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• pp.1-8
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• 2007

This review discusses the production of alpha-particle-emitting radionuclides in radioimmunotherapy. Radioimmunotherapy labeled with alpha-particle is expected to be very useful for the treatment of monocellular cancer (e.g. leukemia) and micrometastasis at an early stage, residual tumor remained in tissues after chemotherapy and tumor resection, due to the high linear energy transfer (LET) and the short path length in biological tissue of alpha particle. Despite of the expected effectiveness of alpha-particle in radioimmunotherapy, its clinical research has not been activated by the several reasons, shortage of a suitable a-particle development and a reliable radionuclide production and supply system, appropriate antibody and chelator development. Among them, the establishment of radionuclide development and supply system is a key factor to make an alpha-immunotherapy more popular in clinical trial. Alpha-emitter can be produced by several methods, natural radionuclides, reactor irradiation, cyclotron irradiation, generator system and elution. Due to the sharply increasing demand of $^{213}Bi$, which is a most promising radionuclide in radioimmunotherapy and now has been produced with reactor, the cyclotron production system should be developed urgently to meet the demand.

• 한국의류학회지
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• 제17권3호
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• pp.380-390
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• 1993

Effect of interfacial electrical conditions on adhesion of ${\alpha}-Fe_2O_3$ particles to PET fabric and the removal of ${\alpha}-Fe_2O_3$ particles from PET fabric, were investigated as functions of pH, electrolyte and ionic strength. The ${\zeta}$ potential of PET fiber and ${\alpha}-Fe_2O_3$ particles in the electrolyte solution were measured by streaming potential and microelectrophoresis methods respectively. The potential energy of interaction between ${\alpha}-Fe_2O_3$ particles and PET fabric were calculated by using the heterocoagulation theory for a sphere-plate model. The negative ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber increased with pH, and then decreased certain pH and isoelectric points of ${\alpha}-Fe_2O_3$ particles and PET fiber were pH 6.5 and pH 3.5, respectively. The negative ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber affected by electrolytes, were relatively high with polyanion electrolytes in solutions and were low with neutral salts. However, at surfactant solution, ${\zeta}$ potential was levelled off. The influence of the ionic strength on the ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle was small but the negative ${\zeta}$ potential of PET fiber increased with the ionic strength. In the presence of anionic surfactant, the ${\zeta}$ potential of ${\alpha}-Fe_2O_3$ particle and PET fiber increased regardless of solution conditions. The interaction energy between ${\alpha}-Fe_2O_3$ particle and PET fabric increased with pH. The interaction energy was relatively high with polyanion electrolytes in solution, and the influence of ionic strength on the interaction energy was small, and the effective thickness of electrical double layer increased with decreasing the ionic strength.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.159-163
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• 1988

The purpose of this paper is to investigate the effects of alpha particles on the memory circuits such as a sense amplifier and bit lines. Sense amplifiers column alpha particle hits have been simulated for a mega bit DRAM using SPICE, a circuit simulation program. The energy of alpha particle and the substrate concentration are found to strongly influence the likehood of soft errors. Our results may be useful for the designing of alpha particle immune sense amplifiers.

• 한국분말재료학회지
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• 제6권3호
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• pp.246-250
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• 1999

The effects of the ${\beta}-Si_3N_4$ starting particle size and $\alpha$/$\beta$ phase transformation during sintering process on the microstructure evolution of Yttrium $\alpha$-Sialon ceramics were investigated. As-received ${\beta}-Si_3N_4$ powder (mean particle size: 0.54$\mu$m) and classified ${\beta}-Si_3N_4$ powder(mean particle size: $0.26\mu{m}$) were used as starting powders. With decreasing the starting particle size, the growth of elongated grains was enhanced, which resulted in the whisker -like microstructure with elongated grains. These results were discussed in relation to the two-dimensional nucleation and growth theory. In the specimen heat treated at $1600^{\circ}C$ for 10h before sintering at $1950^{\circ}C$for 1h under 40atm(2-step sintering), the grain size was smaller than of the 1-step sintering at 195$0^{\circ}C$ for 1h. However, bimodal microstructure evolution were not not remarkable in both sample, which is ascribed to the $\alpha$-phase contents existing in ${\beta}-Si_3N_4$ starting powder.

• 멤브레인
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• 제26권5호
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• pp.372-380
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• 2016

본 연구에서는 입자크기가 다른 3가지 ${\alpha}$-알루미나 분체로부터 주입성형법과 소결법을 혼용하여 튜브형 ${\alpha}$-알루미나 지지체를 제조하여 초기 ${\alpha}$-알루미나 분체의 입자크기와 소결 온도가 지지체의 기공구조와 기체투과 특성에 미치는 영향을 고찰하였다. 평균입경이 0.2, 0.5, $1.7{\mu}m$인 ${\alpha}$-알루미나 분체를 사용했을 시 제조된 ${\alpha}$-알루미나 지지체는 각각 약 80, 130, 200 nm의 평균 기공경을 가졌으며 평균 기공경은 소결 온도 보다는 초기 알루미나 분체의 입자크기에 의존하였다. 모든 시편에서 소결 온도가 증가할수록 지지체의 부피 밀도는 증가하였고 겉보기 기공률은 감소하였다. He, $N_2$, $O_2$, $CO_2$에 대하여 $30^{\circ}C$에서 단일기체 투과 특성을 평가한 결과, 기체 투과도는 기공경 제곱에 비례하여 증가하였고 기공률이 증가함에 따라서 직선적으로 증가하였다. 이를 토대로 제조된 ${\alpha}$-알루미나 지지체의 기체 투과는 점성유동(viscous flow)에 의하여 이루어지며, ${\alpha}$-알루미나 지지체의 기체 투과 특성은 초기 ${\alpha}$-알루미나 분체의 입자크기와 소결온도를 제어함으로써 조절될 수 있음을 확인할 수 있었다.

• 한국의류학회지
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• 제22권8호
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• pp.1132-1140
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• 1998

The adhesion and removal of $\alpha$-Fe2O3 particles on the from PET fabric in NPE solution with different ionic strength were discussed in terms of interaction of surface charge of particle and substrate. The adhesion of $\alpha$-Fe2O3 particles to PET fabric and its removal from PET fabric were carried out by using water bath shaker and Terg-O-Tometer under various solution conditions. The ζ potential of PET fiber and $\alpha$-Fe2O3 particles in the detergent solution were measured by steaming potential and microelectrophoresis methods, respectively. The adhesion and removal amount of $\alpha$-Fe2O3 particles on the from PET fabric increased with increasing time of adhesion and removal, and the rates of adhesion and removal were high at the initial stage of adhesion and removal, and then the rates decreased with passing time. The adhesion and removal amount of $\alpha$-Fe2O3 particles on and from PET fabric increased with increasing pH of solution regardless ionic strength. The tendencies and degree of adhesion and removal were very similar regardless interaction of surface charge of particle and fiber. Therefore, in the presence of a surfactant and electrolyte, the influence of interaction of surface charge of particle and substrate on the detergency of particulate soil was small.

• 한국의류학회지
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• 제28권6호
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• pp.854-861
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• 2004

To estimate dispersion stability of particles in anionic and nonionic surfactant mixed solution, suspending power was examined as functions of duration time of suspension, ionic and nonionic surfactant mixed ratio, surfactant concentration, kinds of electrolyte, ionic strength and mole numbers of oxyethylene additions to nonionic surfactant using $\alpha$-Fe$_2$O$_3$ particle as the model of particulate soil. The suspending power of anionic and nonionic surfactant mixed solution was relatively higher than that of anionic and nonionic surfactant single solution regardless of solution concentration. The suspending power was gradually decreased with increasing duration time of suspension. In the absence of electrolyte, the effect of surfactant concentration on suspending power was small but in solution with electrolyte, suspending power was lowest at 1 ％ surfactant concentration. With 1${\times}$10$^{-3}$ ionic strength and polyanionic electrolyte in solution, the suspending power was high but effects of oxyethylene mole number to nonionic surfactant on suspending power was small. Generally the suspending power was gradually increased with decreasing the particle size. Hence the suspending power was inversely related to the particle size.

• 대한전기학회논문지
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• 제40권7호
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• pp.675-683
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• 1991

When alpha particles are incident into the substrate, we have calculated the advanced current caused by collecting charges as a function of time, the energy of alpha particle, and the carrier concentration of the substrate. Employing SPICE, we have compared two circuits of which one has dummy cell and another has dummy line instead of dummy cell, and both are connected to the bit line node including sense amplifier and cell within the memory device. From the numerical analysis, (it may be conjectured that)the smaller energy of alpha particle and the lower concentration of the substrate, the more possibility of misoperation due to alpha particles. It may be also found that the effects of alpha particle are substantially reduced in the circuit without dummy cell.

• 한국세라믹학회지
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• 제31권11호
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• pp.1307-1314
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• 1994

The aim of this work is to show the way of manufacturing the SiC mechanical seal at the low temperature of 130$0^{\circ}C$ using clay and frit as source of secondary phase. $\alpha$-SiC and $\beta$-SiC powder which showed different distribution of particle were used as starting materials, i.e. average particle size of $\alpha$-SiC was larger than that of $\beta$-SiC. The mechanical and tribological properties of two groups of specimen, i.e. one contained mainly larger $\alpha$-SiC powder and the other mainly fine particle $\beta$-SiC, were measured. The specimen consisted of larger $\alpha$-SiC exhibited lower density flexural strength and wear resistance is comparison with these of sample containning mainly $\beta$-SiC . This difference could be originated from the dependence of capillary force on the particle size. For the larger SiC particle, the liquid phase may not fill the whole pores during sintering, due to low capillary force, whereas the liquid phase can infiltrate into the small ores surrounded small $\beta$-SiC particle. Thus, the course of high flexural strength and high wear resistance of specimen prepared using small particles can be explaced from the easy infiltration of liquid phase.