• Nuclear Engineering and Technology
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• v.49 no.1
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• pp.209-215
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• 2017

Fast neutron irradiation was used to improve the switching speed of a 600-V nonpunch-through insulated gate bipolar transistor. Fast neutron irradiation was carried out at 30-MeV energy in doses of $1{\times}10^8n/cm^2$, $1{\times}10^9n/cm^2$, $1{\times}10^{10}n/cm^2$, and $1{\times}10^{11}n/cm^2$. Electrical characteristics such as current-voltage, forward on-state voltage drop, and switching speed of the device were analyzed and compared with those prior to irradiation. The on-state voltage drop of the initial devices prior to irradiation was 2.08 V, which increased to 2.10 V, 2.20 V, 2.3 V, and 2.4 V, respectively, depending on the irradiation dose. This effect arises because of the lattice defects generated by the fast neutrons. In particular, the turnoff delay time was reduced to 92 nanoseconds, 45% of that prior to irradiation, which means there is a substantial improvement in the switching speed of the device.

• Electrical & Electronic Materials
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• v.7 no.3
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• pp.231-235
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• 1994

The multi-dielectric layer $SiO_2$/$Si_3{N_4}$/$SiO_2$ (ONO) is used to improve charge retention and to scale down the memory device. The nitride layer of MNOS device is oxidize to form ONO system. During the oxidation of the nitride layer, the change of thickness of nitride layer and generation of interface state between nitride layer and top oxide layer occur. In this paper, effects of oxidation of the nitride layer is studied. The decreases of the nitride layer due to oxidation and trapping characteristics of interface state of multi layer dielectric film are investigated through the C-V measurement and F-N tunneling injection experiment using SONOS capacitor structure. Based on the experimental results, carrier trapping model for maximum flatband voltage shift of multi layer dielectric film is proposed and compared with experimental data. As a results of curve fitting, interface trap density between the top oxide and layer is determined as being $5{\times}10^11$~$2{\times}10^12$[$eV^1$$cm^2$].

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.2
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• pp.48-55
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• 2006

Performance characteristics of the position-domain Hatch filter is analyzed for differential global navigation satellite systems. It is shown that the position-domain Hatch filter generates white measurement residual sequences, which is beneficial property for fault detection. It is also shown that the position-domain Hatch filter yields more accurate a priori state estimate than the position-domain Kalman-type filter. Thus, it can be concluded that the position-domain Hatch filter is beneficial in wide application areas where fault-tolerance and accuracy are required at the same time.

• Journal of Information Processing Systems
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• v.10 no.4
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• pp.602-617
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• 2014

The performance of a cognitive radio network (CRN) solely depends on how precisely the secondary users can sense the presence or absence of primary users. The incorporation of a spatial false alarm makes deriving the probability of a correct decision a cumbersome task. Previous literature performed this task for the case of a received signal under a Normal probability density function case. In this paper we enhance the previous work, including the impact of carrier frequency, the gain of antennas on both sides, and antenna heights so as to observe the robustness against noise and interference and to make the correct decision of detection. Three small scale fading channels: Rayleigh, Normal, and Weibull were considered to get the real scenario of a CRN in an urban area. The incorporation of a maximal-ratio combining and selection combing with a variation of the number of received antennas have also been studied in order to achieve the correct decision of spectral sensing, so as to serve the cognitive users. Finally, we applied the above concept to a traffic model of the CRN, which we based on a two-dimensional state transition chain.

• The Journal of Information Technology
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• v.8 no.3
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• pp.105-115
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• 2005

The CMA and MMA blind equalization algorithm has the inevitable large residual error caused by mismatching between the symbol constellation at a steady state after convergence. Stop-and-Go algorithm has a very superior residual error characteristics at a steady state but a relatively slow convergence characteristics. In this paper, we propose a SAG-Flagged MMA as a new adaptive blind equalization algorithm with a Stop-and-Go flag which follows a flagged MMA in update scheme of tap weights as appling the flag obtaining from Stop-and-Go algorithm to MMA. Using computer simulation, it is confirmed that the proposed algorithm has an enhancing performance from the viewpoint of residual ISI, residual error and convergence speed in comparison with MMA and Stop-and-Go algorithm. Algorithm has a new error function using the decided original constellation instead of the reduced constellation. By computer simulation, it is confirmed that the proposed algorithm has the performance superiority in terms of residual ISI and convergence speed compared with the adaptive blind equalization algorithm of CMA family, Constant Modulus Algorithm with Carrier Phase Recovery and Modified CMA(MCMA).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4147-4152
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• 2011

Compared to the constant modulus algorithm (CMA), the modified CMA (MCMA) is easy not only to improve the steady-state performance but also to be expanded to higher-order constellations by using fewer moduli with evenly spaced. In this paper, it is shown that the MCMA is sufficient to achieve satisfactory steady-state performance by applying a variable step-size to the MCMA without switching to an hard decision-directed algorithm. Two new methods varying the step-size are proposed, and the performance improvement of the MCMA with the new methods of variable step-size is presented as compared to the CMA and the fixed step-size MCMA through computer simulations.

• Journal of Power Electronics
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• v.19 no.4
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• pp.907-921
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• 2019

This paper presents two advanced hybrid pulse-width modulation (PWM) strategies for multilevel inverters (MLIs) that provide both common-mode voltage (CMV) elimination and current ripple reduction. The first PWM utilizes sequences that apply one switching state at the double ends of a half-carrier cycle. The second PWM combines the advantages of the former and an existing four-state PWM. Analyses of the harmonic characteristics of the two groups of switching sequences based on a general switching voltage model are carried out, and algorithms to optimize the current ripple are proposed. These methods are simple and can be implemented online for general n-level inverters. Using a three-level NPC inverter and a five-level CHB inverter, good performances in terms of the root mean square current ripple are obtained with the proposed PWM schemes as indicated through improved harmonic distortion factors when compared to existing schemes in almost the entire region of the modulation index. This also leads to a significant reduction in the current total harmonic distortion. Simulation and experimental results are provided to verify the effectiveness of the proposed PWM methods.

• Journal of Electrochemical Science and Technology
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• v.10 no.3
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• pp.321-328
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• 2019

A new miniaturized all solid-state contact Fe (III)-selective PVC membrane electrode based on Fe (II) phthalocyanine as a neutral carrier was described. The effects of the membrane composition and foreign ions on the electrode performance was investigated. The best performance was obtained with a membrane containing 32% poly (vinyl chloride), 64% dioctylsebacate, 3% Fe (II) phthalocyanine, and 1% potassium tetrakis (p-chlorophenyl) borate. The electrode showed near Nernstian response of $26.04{\pm}0.95mV/decade$ over the wide linear concentration range $1.0{\times}10^{-6}$ to $1.0{\times}10^{-1}M$, and a very low limit of detection $1.8{\pm}0.5{\times}10^{-7}M$. The potentiometric response of the developed electrode was independent at pH 3.5-5.7. The lifetime of the electrode was approximately 3 months and the response time was very short (< 7 s). It exhibited excellent selectivity towards Fe (III) over various cations. The miniaturized all solid-state contact Fe (III)-selective membrane electrode was successfully applied as an indicator electrode for the potentiometric titration of $1.0{\times}10^{-3}M$ Fe (III) ions with a $1.0{\times}10^{-2}M$ EDTA and the direct determination of Fe (III) ions in real water samples.

• Journal of Radiation Protection and Research
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• v.48 no.3
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• pp.124-130
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• 2023

Background: When bipolar junction transistors (BJTs) are used as switches, their switching characteristics can be deteriorated because the recombination time of the minority carriers is long during turn-off transient. When BJTs operate as low frequency switches, the power dissipation in the on-state is large. However, when BJTs operate as high frequency switches, the power dissipation during switching transients increases rapidly. Materials and Methods: When silicon (Si) BJTs are irradiated by fast neutrons, defects occur in the Si bulk, shortening the lifetime of the minority carriers. Fast neutron irradiation mainly creates displacement damage in the Si bulk rather than a total ionization dose effect. Defects caused by fast neutron irradiation shorten the lifetime of minority carriers of BJTs. Furthermore, these defects change the switching characteristics of BJTs. Results and Discussion: In this study, experimental results on the switching characteristics of a pnp Si BJT before and after fast neutron irradiation are presented. The results show that the switching characteristics are improved by fast neutron irradiation, but power dissipation in the on-state is large when the fast neutrons are irradiated excessively. Conclusion: The switching characteristics of a pnp Si BJT were improved by fast neutron irradiation.

• Korean Journal of Human Ecology
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• v.9 no.1
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• pp.81-88
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• 2006

IGFs and IGFBPs have an important role in controlling glucose homeostasis. This study was conducted to investigate the changes of insulin-like growth factor(IGF)-I. IGF-II and IGF binding proteins (IGFBPs) on fasting and postprandial state in Korean diabetes, Twenty eight healthy subjects and fifty seven diabetic patients participated in this study. The healthy subjects were not knowingly suffered from any disease and were not receiving any medical treatment, and diabetic subjects were undergo medical treatment, continuously. Weight and height were measured and body mass index (BMI) was calculated as weight (kg) divided by the square of height (m2). Blood pressure was measured. Plasma lipid profiles were analyzed by enzymatic methods, plasma Insulin and glucose levels were measured in fasting and postprandial state, respectively. The levels of serum IGFs and IGFBP-3 were measured by radioimmunoassay (RIA). The levels of glucose and insulin were significantly higher in diabetes than normal subjects on fasting as well as postprandial state (p<0.0l). The levels of IGF-I was significantly lower in diabetes than normal subjects, however in postprandial state, there was no significant difference between diabetes and control subjects, The levels of IGF-II were significantly lower in diabetes than control subjects both fasting and postpradial state, The level of IGFBP-3 were not significantly different between diabetes and normal subjects. Fasting IGF-I, IGF-II and IGFBP-3 levels were positively correlated with those levels on postprandial state, fasting IGe levels of IGF-I levels were positively correlated with fasting insulin levels, and postprandial IGF-I levels were positively correlated with fasting glucose, postprandial insulin and postprandial insulin levels, plasma triglyceride levels were correlated with plasma triglyceride levels. The IGFBP-3 levels were not correlated with IGF components, glucose, insulin and plasma lipids, These results demonstrate that in diabetes, the components IGF-I/IGFBPs system were significantly correlated with plsma glucose and insulin levels both fasting and postprandial state.