• Journal of the Korean Vacuum Society
• /
• v.21 no.6
• /
• pp.342-347
• /
• 2012

The optical properties of InAs quantum dots (QDs) grown on a GaAs substrates by migration enhanced molecular beam epitaxy method have been investigated by using photoluminescence (PL) and time-resolved PL measurements. The luminescence properties of InAs/GaAs QDs have been studied as functions of temperature, excitation laser power, and emission wavelength. The PL peak of InAs QDs capped with $In_{0.15}Ga_{0.85}As$ layer (QD2) measured at 10 K is redshifted about 80 nm compared with that of InAs QDs with no InGaAs layer (QD1). This redshift of QD2 is attributed to the increase in dot size due to the diffusion of In from the InGaAs capping layer. The PL decay times of QD1 and QD2 at 10 K are 1.12 and 1.00 ns taken at the PL peak of 1,117 and 1,197 nm, respectively. The reduced decay time of QD2 can be explained by the improved carrier confinement and enhanced wave function overlap due to increased QD size. The PL decay times for both QD1 and QD2 are independent on the emission wavelength, indicating the uniformity of dot size.

• Journal of IKEEE
• /
• v.25 no.2
• /
• pp.388-398
• /
• 2021

This paper proposes a particle swarm optimization (PSO)-based peak shaving scheme using energy storage system (ESS) for electricity tariff reduction. The proposed scheme compares the actual load with the estimated load consumption, calculates the additional output power that the ESS needs to discharge additionally to reduce peak load, and adds the input. In addition, in order to compensate for the additional power, the process of allocating power to the determined point is performed, and an optimization that minimizes the average of the load expected at the active power allocations using PSO so that the allocated value does not affect the peak load. To investigated the performance of the proposed scheme, case study of small and large load prediction errors was conducted by reflecting actual load data and load prediction algorithm. As a result, when the proposed scheme is performed with the ESS charge and discharge control to reduce electricity tariff, even when the load prediction error is large, the peak load is successfully reduced, and the peak load reduction effect of 17.8% and electricity tariff reduction effect of 6.02% is shown.

• Journal of the Korea Society for Simulation
• /
• v.19 no.3
• /
• pp.37-43
• /
• 2010

In field, one can observe without difficulties that two flocks are intersected or combined with each other. For example, a fish flock in a stream separates into two part by obstacles (e.g. stone) and rejoins behind the obstacles. The dynamics of two flocks guided by their leader were studied in the situation where the flocks cross each other with a crossing angle, ${\theta}$, between their moving directions. Each leader is unaffected by its flock members whereas each member is influenced by its leader and other members. To understand the dynamics, I investigated the order parameter, ${\phi}$, defined by the absolute value of the average unit velocity of the flocks' members. When the two flocks were encountered, the first peak in ${\phi}$ was appeared due to the breaking of the flocks' momentum balance. When the flocks began to separate, the second peak in ${\phi}$ was observed. Subsequently, erratic peaks were emerged by some individuals that were delayed to rejoin their flock. The amplitude of the two peaks, $d_1$ (first) and $d_2$ (second), were measured. Interestingly, they exhibited a synchronized behavior for different ${\theta}$. This simulation model can be a useful tool to explore animal behavior and to develop multi-agent robot systems.

• Journal of the Korean Society of Radiology
• /
• v.18 no.1
• /
• pp.1-9
• /
• 2024

Proton therapy is known for its superior treatment method due to Bragg peak. To enhance the therapeutic effects of protons, research has been conducted on distributing gold nanoparticles within tumors to increase the absorbed dose. While previous studies focused on handling gold nanoparticles at micrometer and nonometer scale, this study proposes a method to computationally estimate the effect of gold nanoparticles at the millimeter scale. The Geant4 toolkit was applied to computational modeling. Assuming a uniform distribution of water, similar to the human body, and gold nanoparticles, the concentration of gold nanoparticles was adjusted using density ratios. When the density ratio was 5%, the gain in absorbed energy due to gold nanoparticles was nearly twice that of the pure water phantom at the Bragg peak. As the density ratio increased, the gain in absorbed energy linearly increased. When gold nanoparticles were distributed in only one voxel at the Bragg peak, the energy of the protons affected only the neighboring voxels. However, in cases where gold nanoparticles were distributed over a wide area, the volume showing 95% of the maximum absorbed energy (9.46 keV) for the pure water phantom (9.95 keV) exhibited an improvement in absorbed energy over a region 16 times larger, and this region increased as the density ratio increased. Further research is needed to quantify the relationship between the density ratio of gold nanoparticles and the relative biological effect (RBE) in the millimeter scale.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 1999.10a
• /
• pp.128-130
• /
• 1999

대기오염물질의 침적현상은 대기 중에 부유하는 독성물질의 거동에 영향을 미치고 대기오염물질이 대기로부터 수면 또는 지표로 이동하는 주요 경로이며 이로 인하여 식물성장에 대한 피해 및 토양오염, 수질오염을 야기시키는 등 환경에 주는 영향으로 인하여 그 중요성과 관심이 증가되고 있다. 대기침적현상에 의한 수체(water body)의 영향정도에 관한 연구결과에 의하면, 미국의 5대호에 있어서 납 총량의 95％ 이상이 대기로부터 기여되고 있으며, 미국동부의 체사피크만(Chesapeake Bay)의 경우 적조현상의 원인물질로 알려진 질소에 대한 대기 기여도가 25∼40％에 이르고 있는 것으로 보고되고 있다.(U.S.EPA., Report 1991)(중략)

• Journal of the Korea Concrete Institute
• /
• v.26 no.4
• /
• pp.555-562
• /
• 2014

To perform performance-based seismic design of buildings, it is necessary clear goal for usage and stability after an earthquake. To clear this goal, it requires a review of the constituent material of the building and, in particular, a member used as an indicator of the residual strain is useful. There are more usage of prestressed concrete because of prestressing steel witch has characteristics of the origin-oriented. In this study, the goal is estimating of residual strain on the prestressed concrete beam member. The expression for angle of deformed prestressed concrete beam member was obtained from using of curvature on the critical section and the equivalent plastic hinge length based on 'equivalent plastic hinge length method'. Considering the balance of strength and deformation conditions, suitable analysis values were derived from 'split Element Method'. Through various parametric studies, various factors affecting the residual strain were decided. Based on the results of this study, it is expected many researches will be proceed in the future.

• Journal of the Korean Chemical Society
• /
• v.35 no.2
• /
• pp.151-157
• /
• 1991

A sensitive stripping voltammetric study of the complex of indium with 8-hydroxyquinoline at a hanging mercury drop electrode was investigated in 0.1M acetate buffer solution. The effects of various analytical conditions on the reduction peak current of the adsorbed complex were discussed. Optimal analytical conditions were found to be the ligand concentration of $2 {\times}10^{-5}$M, solution pH 4.75, scan rate of 10 mV/s, deposition potential of -0.450V, a deposition time of 90 second. Interferences by other trace metals and Triton X-100 were also discussed. Detection limit was 0.2 ppb of indium after 90 sec. Deposition time, and the relative standard deviation(n = 10) at 4 ppb was 3.2%.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
• /
• v.26 no.2
• /
• pp.93-98
• /
• 2020

The blends of Poly(lactic acid) (PLA) and Poly(butylene adipate-co-terephthalate) (PBAT) have been recognized as a replacement for commodity plastic films and bags in biodegradable packaging industries. The purpose of this study is to identify changes in the thermal and mechanical properties of PLA/PBAT blends with the addition of poly(ethylene oxide)(PEO). PLA (80%) and PBAT (20%) were melt mixed with 0 to 10 phr of PEO and processed using a hot press. The addition of PEO into PLA/PBAT increased the elongation at break and improved thermal stability. With PEO addition, two melting temperature (T_m) peaks of PLA/PBAT merged into one peak showing improved miscibility. The result of this study showed that the addition of PEO increased the ductility and thermal stability of PLA/PBAT blends.

• Korean Journal of Food Science and Technology
• /
• v.30 no.6
• /
• pp.1279-1284
• /
• 1998

This study was designed to investigate the reasonable roasting condition of chicory. Extraction and surface color development of roasted chicory were significantly influenced by roasting temperature and time, and they were increased with increasing time, and roasting at $170^{\circ}C$ showed the highest browning color development. Soluble solid contents was not affected by roasting temperature and time. Roasting for 10min at $150^{\circ}C$ exhibited the highest sensory score, at which the free sugar composition of the extract was 0.87% xylose, 0.62% fructose and 0.84% sucrose. A total of 17 volatile components were identified by GC/MSD from the dried and roasted chicories. Aldehyde, ketone and pyrazine compounds were found to be major volatile flavor components in chicory roots. It was concluded that the results of this work will be useful to determine the optimum conditions for roasting of chicory roots.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.13 no.1
• /
• pp.94-101
• /
• 1999

In this paper the problems associated with the switching surge of PWM inverter devices were analysed. As the application of ASD for efficient speed control of AC rmtors is increased, so is the rrntor and ASD-related failure increased. In the industrial rmtor awlications, the introduction of PWM drives can sometmes cause insulation breakdown between the phase windings due to high transient voltage peak. The motor cable length combined with the high switching frequency becomes more sensitive issue for proper drive operation. Effects of the cable length and high switching frequency influence both on rmtor and inverter. When the insulation level of rmtor winding is low, the failure probability caused by high peak voltage and fast voltage rise times(dv/dt) is high. Voltage refloctions are simulated far rmtor capacities, ASD and rise times and are presented graphically. The filtering techniques are discussed to reduce the rmtor terminal overvoltage and dv/dt in inverter fed AC rrntor drive systems. We confirmed that the lower motar capacity and rmtar insulation level, the shorter switching time and cable length and the higrer the probability of insulation breakdown .kdown .