• Journal of the Korean Society of Radiology
• /
• v.7 no.6
• /
• pp.415-418
• /
• 2013

Thermoluminescent dosimeter utilizes the fact that when irradiated specimen is heated up, some part of the absorbed energy is emitted from the specimen as light with longer wavelength. This research aims at analyzing the glow curves of four TLD-100 exposed to a magnetic field and those of other four TLD-100 not exposed to one by treating them with heat and irradiating them, which are commonly used as thermoluminescent dosimeter, in the same condition. As the result of the experiment, regarding the electrons captured by irradiation, some of the electrons of lower traps were combined with positive holes of valence band through the exposure to a magnetic field, and the peak size decreased by 48%. The reduction in the size of the lower traps caused the TLD-100 exposed to a magnetic field to display a low level of dose. In addition, low traps estimated activation energies are 1.6 eV and 1.5 eV.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.1
• /
• pp.58-67
• /
• 1992

Optical absorption and photoluminescences(PL) of MgGa2Se4 and MgGa2Se4 : Co2+ single crustals were guown by the Bridgman method have been investigated in the visible and near-in frared regions. The optical absorption spectrum showed three absorption peak at 760 nm(13158nm, -1, 1.63eV), 1640nm(6097cm-1, 0.75eV).and 2500nm(4000cm-1,0.49eV) which are assigned the electronic transitions between the ground state and excited states of Co2+ ions with Td sym-metry in MgGa2Se4 host lattice. In PL spectrum the visible emission bands as well as the infrared emission band in these single cuystals are obserned. The visible emission bands are explained due to the radiative transitions of electrons from quasi continusly distributed tarps below the bottom of the conduction band to acceptor levels above the top of the valence band in the proposed energy level scheme. At the same time, it is considered that the infrated emission bands are attributed to electron transitions from the deep levels to the acceptor levels. The mechanism of the optical transition os well explained in terms of the energy diagram of MgGa2Se4.

• Korean Journal of Materials Research
• /
• v.13 no.6
• /
• pp.343-346
• /
• 2003

Photoluminescence(PL), photostimulated luminescence(PSL) and thermoluminescence(TL) in $SrC1_2$:$Eu^{2+}$ , $Na^{+}$ phosphor powder were measured, and the activation energies(trap depth) of traps associated with TL and PSL were investigated. The PL and PSL in the studied sample is due to the $4f^{6}$ 5d\longrightarrow$4f^{7}$transition of $Eu^{ 2+}$. TL glow curve is single peak, and its peak temperature is about 377.2 K. The PL, PSL and TL emission spectra of the phosphors are located in the range of 380∼440 nm, peaking at 408 nm. The activation energy of the PSL trapping center is 0.78 eV and that of the TL trapping center is 0.79 eV. We, thus, suggest that the trapping centers giving rise to the PSL are identical to those giving rise to the TL.

• Proceedings of the KOR-BRONCHOESO Conference
• /
• 1991.06a
• /
• pp.15-15
• /
• 1991

한국어 자음에 대한 생리적인 분류는 조음점 및 조음발법에 따라 다시 세분화할 수 있는데 그중에서 조음발법에 따라 파열음, 마찰음, 파찰음 및 비음들 여러가지로 분류할 수 있다. 그중 특히 파열음은 그 개방하는 방법에 따라 연음(lenis), 경음(glottalized) 및 기식음(aspirated)등으로 구분하는데 이러한 각음을 육안으로 확인하면 모음이 발성되기 위한 성대진동이 있기전의 자음을 위한 성대의 운동의 현상을 보면 기식음에서는 성대열림이 가장 크고 연음에서도 열림이 크지만 기식음보다는 적고 경음에서는 성대의 열림이 가장 작았다. 이러한 현상은 후두내시경에 의해 쉽게 확인할 수 있었는데 이것을 과학적으로 규명하기 위해서는 여러연구에 의해 가능하나 흔히 후두근전도 검사에 의한 성대내전근과 외전근의 역할의 차이를 비교함으로서 가능해지리라 예상되어 본 연구를 시행하였다. 사용된 문형 또는 단어는 한가지를 제외하고는 모두 의미있는 단어를 사용하였으며 EMG recording을 위해 사용된 근육은 후두내전근인 Vocalis muscle과 후두외전근인 Posterior cricoarytenoid muscle이 사용되었고 전기신호는 computer data processing system에 의해 분석되어졌다. 결과는 내시경에 의한 성대열림의 거리측정 결과를 분석함과 동시에 후두내근에 대한 근전도검사에 의한 분석을 토대로 하였으며 이를 간단히 설명하면 이제까지 많은 사람들은 한국어 자음에 대한 각각의 특징적인 현상들을 주로 성대내전근의 역할에 의해 규명하였으나 본 결과로는 성대내전근의 역할도 중요하지만 성대외전근의 역할 또한 상호 연관성을 가지면서 매우 중요한 역할을 한다는 점이다.for the Isotropic plates can be used. Use of some coefficients can produce "exact" value for laminates with such configuration.trap with 2.88[eV] deep of injected space charge from the chathode in the crystaline regions. The origin of ${\alpha}$$_2$ peak was regarded as the detrapping process of ions trapped with 0.9[eV] deep originated from impurity-ion remained in the specimen during production process of the material, in the crystalline regions. The origin of ${\beta}$ peak was concluded to be due to the depolarization process of "C=0"dipole with the activation energy of 0.75[eV] in the amorphous regions. The origin of ${\gamma}$ peak was responsible to the process combined with the depolarization of "CH$_3$", chain segment, with the activation energy of carriers from the shallo

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.31 no.4
• /
• pp.198-202
• /
• 2018

In this work, we have investigated the effect of a 30-min thermal anneal at $550^{\circ}C$ on the electrical characteristics of neutron-irradiated 4H-SiC MOSFETs. Thermal annealing can recover the on/off characteristics of neutron-irradiated 4H-SiC MOSFETs. After thermal annealing, the interface-trap density decreased and the effective mobility increased in terms of the on-characteristics. This finding could be due to the improvement of the interfacial state from thermal annealing and the reduction in Coulomb scattering due to the reduction in interface traps. Additionally, in terms of the off-characteristics, the thermal annealing resulted in the recovery of the breakdown voltage and leakage current. After the thermal annealing, the number of positive trapped charges at the MOSFET interface was decreased.

• Journal of IKEEE
• /
• v.27 no.4
• /
• pp.556-560
• /
• 2023

In this study, the impact of Nitrogen implantation process on deep-level defects and lifetime in 4H-SiC Epi surfaces was comparatively analyzed. Deep Level Transient Spectroscopy (DLTS) and Time Resolved Photoluminescence (TR-PL) were employed to measure deep-level defects and carrier lifetime. As-grown Schottky Barrier Diodes (SBDs) exhibited energy levels at 0.16 eV, 0.67 eV, and 1.54 eV, while for implantation SBD, defects at 0.15 eV were observed. This indicates a reduction in defects associated with energy levels Z_1/2 and EH_6/7, known as lifetime killers, as impurities from nitrogen implantation replace titanium and carbon vacancies.

• Journal of Life Science
• /
• v.14 no.1
• /
• pp.131-140
• /
• 2004

T7 bacteriophage gp4 is the replicative DNA helicase that unwinds double-stranded DNA by utilizing dTTP hydrolysis energy. The quaternary structure of the active form of T7 helicase is a hexameric ring with a central channel. Single-stranded DNA passes through the central channel of the hexameric ring as the helicase translocates $5'\rightarrow3'$ along the single-stranded DNA. The DNA unwinding was measured by rapid kinetic methods and showed a lag before the single-stranded DNA started to accumulate exponentially. This behavior was analyzed by a kinetic stepping model for the unwinding process. The observed lag phase increased as predicted by the model with increasing double-stranded DNA length. Trap DNA added in the reaction had no effect on the amplitudes of double-stranded DNA unwound, indicating that the $\tau7$ helicase is a highly processive helicase. Global fitting of the kinetic data to the stepping model provided a kinetic step size of 10-11 bp/step with a rate of $3.7 s^{-1}$ per step. Both the mechanism of DNA unwinding and dTTP hydrolysis and the coupling between the two are unaffected by temperature from $4∼37^{\circ}C$. Thus, the kinetic stepping for dsDNA unwinding is an inherent property of tile replicative DNA helicase.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.1
• /
• pp.263-272
• /
• 2011

Highly luminescent and monodisperse InP quantum dots (QDs) were prepared by a non-organometallic approach in a non-coordinating solvent. Fatty acids with well-defined chain lengths as the ligand, a non coordinating solvent, and a thorough degassing process are all important factors for the formation of high quality InP QDs. By varying the molar concentration of indium to ligand, QDs of different size were prepared and their absorption and emission behaviors studied. By spin-coating a colloidal solution of InP QD onto a silicon wafer, InP QD thin films were obtained. The thickness of the thin films cured at 60 and $200^{\circ}C$ were nearly identical (approximately 860 nm), whereas at $300^{\circ}C$, the thickness of the thin film was found to be 760 nm. Different contrast regions (A, B, C) were observed in the TEM images, which were found to be unreacted precursors, InP QDs, and indium-rich phases, respectively, through EDX analysis. The optical properties of the thin films were measured at three different curing temperatures (60, 200, $300^{\circ}C$), which showed a blue shift with an increase in temperature. It was proposed that this blue shift may be due to a decrease in the core diameter of the InP QD by oxidation, as confirmed by the XPS studies. Oxidation also passivates the QD surface by reducing the amount of P dangling bonds, thereby increasing luminescence intensity. The dielectric properties of the thin films were also investigated by capacitance-voltage (C-V) measurements in a metal-insulator-semiconductor (MIS) device. At 60 and $300^{\circ}C$, negative flat band shifts (${\Delta}V_{fb}$) were observed, which were explained by the presence of P dangling bonds on the InP QD surface. At $300^{\circ}C$, clockwise hysteresis was observed due to trapping and detrapping of positive charges on the thin film, which was explained by proposing the existence of deep energy levels due to the indium-rich phases.

• Proceedings of the KIEE Conference
• /
• 1988.11a
• /
• pp.372-375
• /
• 1988

The III-V ternary alloy semiconductor $In_{l-x}Ga_{x}As$ were grown by the temperature Gradient of $0.60{\leq}x{\leq}0.98$. The electrical properties were investigated by the Hall effect measurement with the Van der Pauw method in the temperature range of $90{\sim}300K$. $In_{l-x}Ga_{x}As$ were revealed n-type and the carrier concentration at 300K were in the range of $9.69{\times}10^{16}cm^{-3}{\sim}7.49{\times}10^{17}cm^{-3}$. The resistivity was increased and the carrier mobility was decreased with increasing the composition ratio. The optical energy gap determined by optical transmission were $20{\sim}30meV$ lower than theoretical valves on the basis of absorption in the conduction band tail and it was decreased with increasing the temperature by the Varshni rule. In the photoluminescence of undoped $In_{l-x}Ga_{x}As$ at 20K, the main emission was revealed by the radiative recombination of shallow donor(Si) to acceptor(Zn) and the peak energy was increased with increasing the composition, X. The diffusion depth of Zn increases proportionally with the square root of diffusion time, and the activation energy for the Zn diffusion into $In_{0.10}Ga_{0.90}As$ was 2.174eV and temperatures dependence of diffusion coefficient was D = 87.29 exp(-2.174/$K_{B}T$). The Zn diffusion p-n $In_{x}Ga_{x}As$ diode revealed the good rectfying characteristics and the diode factor $\beta{\approx}2$. The electroluminescence spectrum for the Zn-diffusion p-n $In_{0.10}Ga_{0.90}As$ diode was due to radiative recombation between the selectron trap level(${\sim}140meV$) and Zn acceptor level(${\sim}30meV$). The peak energy and FWHM of electroluminescence spectrum at 77K were 1.262eV and 81.0meV, respectively.

• Journal of Energy Engineering
• /
• v.17 no.4
• /
• pp.189-197
• /
• 2008

In this study, a system to measure continuously the fuel concentration in a steady flow rig on the basis of Rayleigh scattering is presented. The system can be employed to measure both the temporal and the spatial distribution. Also, it is possible to calibrate the system for the measurement of accurate absolute concentration. Firstly, the system was tested at a calibration chamber for the determination of scattering cross section from propane, butane, acetylene, Freon-12 and Genetron 143a. After this, the system was adapted to a steady flow rig to measure the temporal and spatial fuel concentration. The rig is composed of cylinder head, intake manifold, injector, and transparent cylinder which can simulate internal combustion engine. To cope with the interference of Mie scattering, which is main obstacle of the measuring concentration with Rayleigh scattering, a hardware filter was installed for reducing the number density of particles. Furthermore a software filter was developed, which is based on the rise time and the time constant of the photomultiplier-amplifier system. In addition, background noisy was reduced by adjusting the optical array and applying the pin hall and beam trap. The results show that LRS can provide useful information about concentration field and the software filter is very effective method to remove Mie interference.