• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.415-418
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• 2002

We have studied electro-optic properties and layer deformations in the smectic phases of 4-(6ethoxy-l-trifluoromethyl-hexyloxycarbonyl)-phenyl-4-Nonyloxybiphenyl-4-carboxylat ( TFMEOHPNBC ) having fluorine attached to one of its benzene rings by electro-optical and small angle x-ray scattering techniques. 3 and 5${\mu}m$ thick test cells were prepared using beryllium plates to minimize x-ray beam absorption. Layer structure and orientation was studied while changing the amplitude and frequency of the applied electric field as a function of cell temperature. We observed that the chevron layer tilt angle is reduced and layer spacing is increased as stabilizing in antiferroelectric phase. This result is extraordinary that there is dimerization in antiferroelectric phase. We also found that there is a threshold electric field that changes the chevron structure to bookshelf structure. This threshold electric field depends on the frequency and temperature as shown in Fig.1. We will discuss the dynamics of layer orientation as determined from the x-ray, electro-optic and dielectric spectroscopy.

• Bulletin of the Korean Chemical Society
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• v.29 no.4
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• pp.731-735
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• 2008

The fluid ensemble in the liquid lens, which is composed of electrolyte and silicone oil, is the key material system to vary the focal length processing of the electrochemical desorption. In order to characterize the capability of the liquid lens according to response time and optical range, we prepared a fluid ensemble comprising the electrolyte and oil. To elucidate the physical mechanism of the effective response time, we examined the viscosity dependency while satisfying the requirements for the density and refractive index of the electrolyte and oil, respectively. The characterization results indicated that the response time (up and down) is influenced by the viscosity of the electrolyte and oil. On this basis, we prepared a fluid ensemble capable of reversibly adjusting for the focal length of the liquid lens, as well as the response time. The ensemble is applicable to various systems such as micro-lens and optical sensors.

• Journal of Photoscience
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• v.5 no.3
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• pp.125-129
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• 1998

Occurrence of an electron (or H atom equivalent to one electron plus H+) transfer from $\alpha$- tocopherol $\alpha$(TOH) to a number of photosensitizers in theri triplet states were investigated by monitoring the ESR signal of $\alpha$-chromaoxyl radical ($\alpha$(TO.) in ethanolic solutions of $\alpha$TOH and the sensitizers under continuous illumination. Every sensitizer molecule examined, such as protocholorophyllide (Pchl), hematoporphyrin and rose bengal which are generally regarded as efficient type II photosensitizers and thus have long-lived triplet states, was found to actively participate in an electro transfer reaction with $\alpha$TOH even under air-saturation conditions, generating $\alpha$TOH complex as an intermediate in a fashion of Michaelis-Menten type of reaction. For the reaction of $\alpha$TOH with triplet Pchl, the rate law was derived by applying the steady approximation for the binary complex, triplet Pchl-$\alpha$TOH , which turned out to be well consistent with the kinetic data.

• Bulletin of the Korean Chemical Society
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• v.28 no.1
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• pp.81-84
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• 2007

Ab initio periodic Hartree-Fock calculations with the full potential and minimum basis set are applied to interpretation of scanning tunneling microscope (STM) and atomic force microscope (AFM) images on 1TVTe2. Our results show that the simulated STM image shows asymmetry while the simulated AFM image shows the circular electron densities at the bright spots without asymmetry of electron density to agree with the experimental AFM image. The bright spots of both the STM and AFM images of VTe2 are associated with the surface Te atoms, while the patterns of bright spots of STM and AFM images are different.

• Bulletin of the Korean Chemical Society
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• v.24 no.11
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• pp.1671-1674
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• 2003

The effects of amine donors ($a:NH_2,\;b:NMe_2,\;c:NMePh,\;d:NPh_2$) and conjugation length on the molecular hyperpolarizabilities of a series of dipolar molecules have been theoretically investigated by using CPHF/6-31G method. The first hyperpolarizabilities (${\beta}$) of p-nitrobenzene derivatives increase with the donor in the order, $NH_2\;<\;NMe_2\;<\;NMePh\;<\;NPh_2$, whereas slightly different order is observed in more conjugated derivatives, i.e., $NH_2\;<\;NPh_2\;<\;NMe_2\;<\;NMePh$. The result has been attributed to the extent of charge transfer and torsion angle. Moreover, the results show that "non-traditional" ${\pi}$-conjugation effect exists in small compounds and decreases as the conjugation length between donor and acceptor increases.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.104-111
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• 2003

Micro force measurement is required more frequently for a precision manufacturing and investment in fields of precision industries such as semiconductor, chemistry and biology, and so forth. Null balance method has been introduced as an alternative of a loadcell. Loadcells have advantages in aspects of low cost and easy manufacturing, but have also the limitation in resolution and sensitivity to environment variations. In this paper, null balance method is explained and the dominant parameters related to system performances are mentioned. Null position sensor, electromagnetic system and controller are investigated. Also, the characteristic experiment is carried out in order to estimate the resolution and the measurement range. In order to overcome the limitation by the drift of position sensor and the performance of controller, double electromagnetic force compensation method is proposed and experimented. After controlling and filtering, the resolution under $\pm$ 1mg and measurement range over 300g could be obtained.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1510-1512
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• 1997

Piezoelectric characteristics of lead zirconate(PZ)-lead titanate(PT)-lead manganese antimony(PMS) ceramics with the various changes of calcination temperature in PMS were prepared. The range of their sintering temperature was from $1100^{\circ}C$ to $1250^{\circ}C$. The electro-mechanical properties of PZ-PT-PMS ceramics such as piezoelectric constant, electro-mechanical coupling coefficient, and mechanical quality factor are measured as a function of the calcination temperature of PMS. As increasing the calcination temperature of PMS mechanical quality factor is increased.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.168-172
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• 2006

Single pulse of 2.0 to 3.5 kJ from $150{\mu}F$ capacitor was applied to the cp Ti rod for its surface modification and heat treatment. Under the conditions of using 2.0 and 2.5 kJ of input energy, no phase transformation has been occurred. However, the hardness and tensile strength decreased and the elongation increased after a discharge due to a slight grain growth. By using more than 3.0 kJ of input energy, the electro discharge made a phase transformation and the hardness at the edge of the cross section increased significantly. The Ti rod before a discharge was lightly oxidized and was primarily in the form of $TiO_2$. However, the surface of the Ti rod has been instantaneously modified by a discharge into the main form of TiN from $TiO_2$. Therefore, the electro discharge can modify its surface chemistry in times as short as $200{\mu}sec$ by manipulating the input energy, capacitance, and discharging environment.

• Analytical Science and Technology
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• v.6 no.3
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• pp.247-254
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• 1993

Strontium can not be determined by conventional dc polarography method since it is very difficult to be reduced at the drop mercury electrode(DME) in aqueous solution. However the analytical sensitivity was improved by adsorptive stripping voltammetry in which electro-reduction of ligand in a complex formed between strontium and o-cresolphthaleoxone was performed. Strontium could be determined in range of $5{\sim}30{\mu}g/L$ concentration. This method was affected by coexistent alkali earth metal ions. Consequently ion exchange separation is recommended to analyze strontium in samples.

• Bulletin of the Korean Chemical Society
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• v.26 no.1
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• pp.57-62
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• 2005

The potentiometric responses for various anions are investigated with membrane electrode (membrane 1) based on 1,3-diethyl-1,3-dihydroxy-1,3-bis(2-dimethylaminomethyl ferrocenyl) disiloxane. The nitrate ion-selective electrode based on compound 1 gave a good Nernstian response of 58.18 mV per decade for nitrate with the detection limit of −e5.66 of log [NO3−e]. Compound 1 has all those functional groups and the other two compounds have less functional group of ferrocenyl or ferrocenyl and hydroxide, respectively. Even though, potentiometric response to anions was excellent at pH 5, the selectivity pattern for all three membrane electrode based on series of disiloxane is almost like Hofmeister sequence at pH 5. However, the membrane electrode 1-3 exhibited very different response to anions at pH 7. In this pH, NH2 is not protonated and ionophore may act as neutral carrier. Hydrogen bond may enhance the responsibility to hydrogen acceptors and intramolecular electro-active site may increase the permeability of analyte to ionophore in membrane.