• Journal of the Optical Society of Korea
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• v.9 no.2
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• pp.39-44
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• 2005

Unlike for the bound states, several different boundary conditions are used for the continuum states above the barrier in semiconductor quantum wells. We employed three boundary conditions, infinite potential barrier boundary condition, periodic boundary condition and scattering boundary condition, and calculated the local number of states, wavefunctions and optical matrix elements for the symmetric and asymmetric quantum wells. We discussed how these quantities are related in the three boundary conditions. We argue that the scattering boundary condition has several advantages over the other two cases. These results would be useful in understanding quantum well lasers and detectors involving continuum states.

• Proceedings of the KSR Conference
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• 2003.05a
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• pp.68-81
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• 2003

Rockfall protection fence is one of the most common rockfall protection methods in Korea. If rockfall protection fences are required along the road or railway, their location, height and capacity, in terms of the maximum kinetic energy that they can absorb, should be specified. Within this paper, the best practice of rockfall barrier is introduced. Modern rockfall simulations as a means to define risks, protection requirements, dynamic loading and height of potential structures and selection of appropriate placement is presented. Technical possibilities of rockfall barriers and their actual limits are presented. Safety concepts based on probabilities approaches are proposed. Recent studies performed in other countries show that Flexible Barriers are also a feasible system to stop and retain debris flows. Finally an outlook onto further development is given.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.391-395
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• 1986

MNDO calculations were carried out to determine reactant complexes and transition states of the $S_N2$ reactions of $CH_3X\;+\;Y^-\;{\to}\;CH_3Y\;+\;X^-$ where X = F, Cl, CN and Y = CN, OH, F, Cl. The leaving group ability was found to vary inversely with the activation barrier, which in turn was mainly ascribable to the deformation energies accompanied with bond stretching of C-X bond and inversion of $CH_3$ group. The nucleophilicity was shown to be in the order $Cl^->F^->OH^->CN^-$ but the effect on the activation barrier was relatively small compared with that of the leaving group. The bond breaking and bond formation indices and energy decomposition analysis showed that the TS for the reaction of $CH_3$Cl occurs in the early stage of the reaction coordinate relative to that of $CH_3$F. It has been shown that the potential energy surface (PES) diagrams approach can only accommodate thermodynamic effects but fails to correlate intrinsic kinetic effects on the TS structure.

• Bulletin of the Korean Chemical Society
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• v.18 no.11
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• pp.1186-1191
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• 1997

Solvolyses of methanesulfonyl chloride (CH3SO2Cl) in water and methanol have been studied theoretically using ab initio self-consistent reaction field (SCRF) molecular orbital method. All stationary structures including transition state on the potential energy surface in solution have been found and compared with the gas phase structures. The overall reaction occurs via a concerted SN2 mechanism with a non-cyclic trigonal bipyramidal transition state, and the activation barrier is lowered significantly in solution. The transition state for the hydrolysis reaction is looser than that for the methanolysis reaction, and this is in accord with the experimental findings that an SN2 type mechanism, which is shifted toward an SN1 process or an SAN process in the hydrolysis and alcoholysis reaction, respectively, takes place. The catalytic role of additional solvent molecules appears to be a purely general-base catalysis based on the linear transition structures. Experimental barrier can be estimated by taking into account the desolvation energy of nucleophile in the reaction of methanesulfonyl chloride with bulk solvent cluster as a nucleophile.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.8 no.1
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• pp.17-23
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• 2022

Boron neutron capture therapy is a precision treatment technology that selectively destroys only tumor cells by irradiating thermal neutrons after accumulating boron drugs in tumor cells. Brain tumor is difficult to diagnose and treat due to the low permeability and targeting of drugs caused by the blood-brain-barrier. Crossing the BBB is essential for drug delivery to the brain. In this study, we designed and synthesized a novel compound incorporating benzothiazole to develop a boron drug with high BBB permeability and selectivity for brain tumor cells. In addition, their potential as a BNCT drugs was evaluated.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.933-935
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• 2003

Geo-scientifically viable, environmentally suitable, and socially acceptable sanitary landfill sites are very limited in the Kathmandu Valley and is confronted with the burning problem of safe disposal of urban waste. This paper deal with the evaluation and assessment of its interface, following the major criteria defining suitable geological barrier, Cation Exchange Capacity and other necessary physical parameters with the optimum utilization of remotely sense data along with GIS techniques. The study revealed one of the most viable sites at the flat land of natural depression of Taikabu area and has potential to serve all the municipalities of the Kathmandu Valley.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.4
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• pp.785-796
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• 2009

In this paper, propose for mobile robot path planning and the reduction in sleep caused by a sleep history suggested a way to compensate for record sensor error. The proposed path plan reduces the robot slip to smooth a potential barrier in the potential field method, and compensates the tachometer error by robot slip using the fuzzy logic system. The efficiency of the proposed method is verified by means of simulations and experiments for path plan and slip revision.

• Journal of information and communication convergence engineering
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• v.7 no.3
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• pp.361-365
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• 2009

This paper has been presented the transport characteristics of FinFET using the analytical potential model based on the Poisson's equation in subthreshold and threshold region. The threshold voltage is the most important factor of device design since threshold voltage decides ON/OFF of transistor. We have investigated the variations of threshold voltage and drain induced barrier lowing according to the variation of geometry such as the length, width and thickness of channel. The analytical potential model derived from the three dimensional Poisson's equation has been used since the channel electrostatics under threshold and subthreshold region is governed by the Poisson's equation. The appropriate boundary conditions for source/drain and gates has been also used to solve analytically the three dimensional Poisson's equation. Since the model is validated by comparing with the three dimensional numerical simulation, the subthreshold current is derived from this potential model. The threshold voltage is obtained from calculating the front gate bias when the drain current is $10^{-6}A$.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.162-163
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• 2000

We have observed the short-channel effect, narrow-channel effect and small-geometry effect in terms of a variation of the threshold voltage. For a short-channel effect the threshold voltage was largely determined by the DIBL effect which stimulates more carrier injection in the channel by reducing the potential barrier between the source and channel. The effect becomes more significant for a shorter-channel device. However, the potential, field and current density distributions in the channel along the transverse direction showed a better uniformity for shorter-channel devices under the same voltage conditions. The uniformity of the current density distribution near the drain on the potential minimum point becomes worse with increasing the drain voltage due to the enhanced DIBL effect. This means that considerations for channel-width effect should be given due to the variation of the channel distributions for short-channel devices. For CCDs which are always operated at a pinch-off state the channel uniformity thus becomes significant since they often use a device structure with a channel length of > 4 ${\mu}{\textrm}{m}$ and a very high drain (or diffusion) voltage. (omitted)

• Restorative Dentistry and Endodontics
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• v.25 no.1
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• pp.144-152
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• 2000

Intracoronal bleaching is currently disregarded by many clinicians because of the potential consequence of cervical resorption. To prevent this complication it is recommended that intra coronal barrier materials be placed over the root canal obturation and sodium perborate be used with water rather than with hydrogen peroxide. The purpose of this study was to evaluate the amount of the hydrogen peroxide penetration according to the difference in intracanal base materials and sodium perborate preparation. Fifty extracted intact premolars were instrumented, and filled with gutta-percha. And then the outer surface of the teeth was sealed with wax exposing the CEJ. The prepared teeth were placed in plastic tubes containing 1.5ml distilled water with their entire root submerged into the solution, The teeth were divided into the following five groups. In the first two groups gutta-percha was removed without placement of barrier, and then water or superoxole(30% $H_2O_2$) with sodium perborate were used respectively for bleaching. In the other three groups, after removal of gutta-percha, an intracanal isolating barrier(ZPC, IRM, Fuji II LC) was placed and then bleached with sodium perborate and superoxole. The bleaching procedure was performed 4 times with 1 week interval. The results were as follows : 1. All the groups showed a tendency of increasing penetration amount with increasing treatment times(P<0.05). 2. After the 1st and 2nd treatments, there was no significant difference in microleakage among the groups. 3. After the 3rd bleaching with superoxole and sodium perborate, there was no significant difference in microleakage between gutta-percha alone group and gutta-percha with ZPC, Fuji II LC barrier group. But significant difference was found between IRM barrier group and other groups(P<0.01). 4. After the 4th bleaching with superoxole and sodium perborate, there was no significant difference between gutta-percha alone group and gutta-percha with barrier groups. 5. After the 4th treatment, the group bleached with sodium perborate and water without barrier showed lower hydrogen peroxide penetration than that of other groups(P<0.01).