• 오토저널
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• 제11권6호
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• pp.48-56
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• 1989

A shock tube technique was developed in which a freely falling droplets column produced by an ultrasonic atomizer was ignited behind reflected shock. In the present study, the effects of turbulent mixing on the ignition delay of a cetane was decided, also, ignition process was investigated. For the purpose of disturbance of droplets column and mixing, authors installed turbulent lattice in shock tube. Usually, the ignition delay is so called Arrhenius plot which found break point in the Arrhenius plot on the high temperature side. The rate of misfiring increased rapidly below 1080K, but ignition took place from 838k and luminous flame was seen to spread over the whole section by turbulent lattice. Length, from end plate to turbulent lattice, was varied with 60,40,20mm. Also, ignition process was detected by Photo transistor. As a result, it was found that physical factors changed ignition delay greatly and turbulent mixing had a considerable effects in the ignition process.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.150.2-150.2
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• 2011

Unlike non-ionic clathrate hydrates stably formed by van der Waals interaction between a guest molecule and a surrounding host framework, ionic clathrate hydrates are stabilized by ionic interaction between an ionic guest molecule and the host water-framework. Here, we firstly described the stable entrapment of the superoxide ions in ${\gamma}$-irradiated $Me_4NOH+O_2$ hydrate. Owing to peculiar direct guest-guest ionic interaction, the lattice structure of ${\gamma}$-irradiated $Me_4NOH+O_2$ hydrate shows significant change of lattice contraction behavior even at relatively high temperature(120K). Particularly, we note that ionic-induced dimensional change is much greater than thermal-induced change. Such findings are expected to provide useful information for a better understanding of unrevealed nature of clathrate hydrate fields.

• 대한의용생체공학회:의공학회지
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• 제17권2호
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• pp.247-254
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• 1996

The relationship between the isothermal age-hardening behavior and the phase transformation in the commercial dental Au-Ag-Cu-Pd alloy was investigated Age-hardening was mostly attributed to the lattice distortions of the supersaturated w phase resulting from the transformation to the metastable phasel which were more distinct at lower aging temperature. The lattice distortions resulting from the transformation of the metastable phases to the equilibrium phases also made a contribution to the age-hardening.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 추계학술대회 논문집
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• pp.157-161
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• 2000

Blue phosphor of Ba-Mg-Al-O:Eu$^{2+}$ phase was fabricated by conventional firing techniques under reducing atmosphere and its photoluminescence properties are studied with varying Eu concentration and phost-annealing temperature under air atmosphere. This phosphors were well crystallized with particle size in the range of 3~5um and emitted a blue light at a dominent wavelength 450nm for 254nm UV irradiation. The concentration quenching wit Eu$^{2+}$ was that with increasing Eu concentration the energy transfer between the activator ions steadily improves, so that the excitation energy is transported over larger distances through the lattice before luminescence can occur. Thermal quenching also occurred in this phosphor means that in a host lattice with the $\beta$-alumina structure the bond of an Eu$^{2+}$ ion with the nearest-neighbour oxygen ion is much stronger than in a lattice with the magnetoplumbite structure.cture.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.168.2-168.2
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• 2015

We observed the temperature-dependent evolution and behavior of P3HT type-II phase during a real time annealing process from a cryo-cooled low temperature in the absence and presence of an Al electrode. A poly (3-hexylthiophene) (P3HT) Type-II phase in the P3HT:PCBM films started to form near at $-10^{\circ}C$, regardless of Al layer presence. In the absence of an Al layer, type-II phase was extinct at $30^{\circ}C$. However, the extinction temperature was extended to $50^{\circ}C$ in the presence of the Al layer. Simultaneously, combined with the type-II phase, a 1:3 ordered P3HT type-II (1/3,0,0) super-lattice peak evolved. These type-II domains tended to be formed near the Al electrode layer with higher aligned status than host P3HT crystals.

• 한국초전도ㆍ저온공학회논문지
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• 제20권2호
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• pp.24-28
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• 2018

To understand the effects of Cd substitution for Cu, $(Pb_{0.5}Cu_{0.5-x}Cd_x)Sr_2(Ca_{0.7}Y_{0.3})Cu_2O_z$ (x = 0 ~ 0.5) compounds were synthesized and the structural and superconducting properties of the compounds were characterized. Resistivity data revealed that superconducting transition temperature rises initially up to x = 0.25 and then decreases as the Cd doping content increases. Room-temperature thermoelectric power decreases at first up to x = 0.25 and then increases with higher Cd doping content, indicating that the change in $T_c$ is mainly caused by the change in the hole concentration on the superconducting planes by the Cd doping. The non-monotonic dependence of the lattice parameters and the transition temperature with Cd doping content is discussed in connection with the possible formation of $Pb^{+2}$ ions and the removal of excess oxygen caused by Cd substitution in the charge reservoir layer. A correlation between transition temperature and c/a lattice parameter ratio was observed for the $(Pb_{0.5}Cu_{0.5-x}Cd_x)Sr_2(Ca_{0.7}Y_{0.3})Cu_2O_z$ system.

• 한국세라믹학회지
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• 제24권3호
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• pp.263-269
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• 1987

It is investigated that the determination of the correlation between the change of microstructure and electrical properties. Yttria is added to the compositiojn of rhombohedral region in Pb(Mg1/3Nb2./3)O3-PbTiO3-PbZrO3 ternary system. Average grian size, lattice parameters and distribution of yttrium are characterized by XRD, SEM and EDS. Electrical properties are determined by measurement of Curie temperature, piezoelectric properties and hysteresis loops. The results are as follows; 1. Both lattice parameters, a and ${\alpha}$, are changed by addition of yttria to the composition of rhomboheadral region in Pb(Mg1/3Nb2./3)O3-PbTiO3-PbZrO3 ternary system and Curie temperature is proportional to the values at (90-${\alpha}$).

• 한국자기공명학회논문지
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• 제17권1호
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• pp.19-23
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• 2013

The temperature dependences of the NMR spectrum and the spin-lattice relaxation times in $KH_2PO_4$ were investigated via single-crystal NMR and MAS NMR. The stretched-exponential relaxation that occurred because of the distribution of correlation times was indicative of the degree of the distribution of the double-well potential on the hydrogen bond. The behaviors responsible for the strong temperature dependences of the $^1H$ and $^{31}P$ spin-lattice relaxation times in the rotating frame $T_{1{\rho}}$ in $KH_2PO_4$ are likely related to the reorientational motion of the hydrogen-bond geometry and the $PO_4$ tetrahedral distortion.

• 한국세라믹학회지
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• 제33권10호
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• pp.1131-1137
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• 1996

The dielectric properties and phase stabilities of Pb(Zn0.6Mg0.4)1/3Nb2/3O3 [PZMN]system were investigated into substitution of A-site with Ba, Sr and Ca ions. The A-site substitutions led to the complexity of components of perovskite phase and then DPT coefficient increased. The A-site substitutions of Ba or Sr ion perovskite single phase could be easily formed by columbite process due to increase of perovskite phase stability. The variation of lattice parameters in specimen obeyed Vegard's law and curie temperature and dielectric constant of specimen decreased linearly. But Ca substitution led to perovskite phae instability. The lattice parameter dielectric constant and curie temperature of specimens drasticaly decreased with formation of pyrochlore phase.

• Journal of Magnetics
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• 제10권2호
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• pp.63-65
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• 2005

The $^1H$ NMR spin-lattice relaxation in a series of the organic-inorganic hybrid systems $(C_nH_{2n+1}NH_3)_2SnCl_6$ (n = 8, 10, 12, 14) undergoing two successive phase transitions was studied. A discontinuity characteristic of a first order phase transition was observed at the high-temperature conformational transition. Besides, the spin-lattice relaxation rate below the conformational transition temperature was well fitted by four types of molecular motions, from which the chain-length dependence of the activation energies of the molecular groups was obtained.