• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.5
• /
• pp.613-623
• /
• 2012

In this paper, we present an ultra miniaturized voltage tuned oscillator, with HMIC-type amplifier and phase shifter, using LTCC artificial dielectric resonator. ADR which consists of periodic conductor patterns and stacked layers has a smaller size than a dielectric resonator. The design specification of ADR is obtained from the design goal of oscillator. The structure of the ADR with a stacked circular disk type is chosen. The resonance characteristic, physical dimension and stack number are analyzed. For miniaturization of ADRO, the ADR is internally implemented at the upper part of the LTCC substrate and the other circuits, which are amplifier and phase shifter are integrated at the bottom side respectively. The fabricated ADRO has ultra small size of $13{\times}13{\times}3mm^3$ and is a SMT type. The designed ADRO satisfies the open-loop oscillation condition at the design frequency. As a results, the oscillation frequency range is 2.025~2.108 GHz at a tuning voltage of 0~5 V. The phase noise is $-109{\pm}4$ dBc/Hz at 100 kHz offset frequency and the power is $6.8{\pm}0.2$ dBm. The power frequency tuning normalized figure of merit is -30.88 dB.

• Journal of the Korean Ceramic Society
• /
• v.32 no.5
• /
• pp.626-634
• /
• 1995

The SiC-porcelain powder mixtures containing 51.9wt% SiC are produced as by-products from the surface abrasion process of porcelain cores. This raw powders were used as starting materials for the synthesis of SiC containing ceramics. The specimen, which was fired at 135$0^{\circ}C$ from raw powders, had SiC, $Al_{2}O_{3}$, , cristobalite, mullite as crystalline phases, and the fractured microstructure showed dispersed SiC crystalline particles almost wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts wetted with glassy matrix and spherical pores. Although the oxidation of SiC containing powder compacts started at the range of 600~80$0^{\circ}C$ form the analysis of weight gain, the presence of $SiO_{2}$ crystallien phase and cristobalite was confirmed at 100$0^{\circ}C$ by XRD analysis. Mullitization of specimens was accelerated by preheating before the final firing. The specimen sintered at 135$0^{\circ}C$ after 100$0^{\circ}C$ preheating consisted of SiC, cristobalite, mullite as crystalline phases, and revealed 2.24g/$cm^{3}$ bulk density, 11.73% water adsorption, porous microstructure with small amount of glassy phase. SiC contents of specimens, which was 51.9 wt% in the raw powders, reduced to 37~22 wt% after firing at 135$0^{\circ}C$ depending on the preheating condition.

• Journal of Biomedical Engineering Research
• /
• v.25 no.6
• /
• pp.611-615
• /
• 2004

A neural prostheses can be designed to permit stimulation of specific sites in the nervous system to restore their functions, lost due to disease or trauma. This study focuses on the feasibility of optoelecronic stimulation into nervous system. Optoelectronic stimulation supplies, power and signal into the implanted optical detector inside the body by optics. It can be effective strategy especially on the retinal prosthesis, because it enables the non-invasive connection between the external source and internal detector through natural optical window 'eye'. Therefore, we designed an effective neural stimulating setup by optically based stimulation. Stimulating on the sciatic nerve of a rat with proper depth probe through optical stimulation needs higher ratio of current spreading through the neural surface, because of high impedance of neural interface. To increase the insertion current spreading into the neuron, we used a parallel low resistance compared to load resistance organic interface and calculated the optimized outer parallel resistance for maximum insertion current with the assumption of limited current by photodiode. Optimized outer parallel resistance was at a range of 500Ω-700Ω and a current was at a level between 580uA and 650uA. Stimulating current efficiency from initial photodiode induced current was between 47.5 and 59.7%. Various amplitude and frequency of the optical stimulation on the sciatic nerve showed the reliable visual tremble, and the action potential was also recorded near the stimulating area. These result demonstrate that optoelectronic stimulation with no bias can be applied to the retinal prosthesis and other neuroprosthetic area.

• The Korean Journal of Air & Space Law and Policy
• /
• v.22 no.2
• /
• pp.3-25
• /
• 2007

In 2002 Republic of Korea successfully launched a self-made mined proportion rocket and it is expected that she will be able to have own space launching system by 2010. According to Article 14 of the Space Exploration Promotion Act, a new law should be established to impose the limit of compensation for the damage by space accident. Therefore, The Space Accident Liability Act was passed in Korean Congress on Nov. 22, 2007 and it will be enforced in six months. The purpose of this Act is to provide reparation for the damage of the third parties that a launch causes; and the Commonwealth should be insured against any possible space accidents to pay for such a damage. Here space accident means the damages to our life, body, and properties from the launching of space objects. There should be an actual loss to establish the compensation of Liability Act. Article 2 in Liability Act defines "damage" as follows: the term "damage" means loss of life, personal injury or loss of or damage to property of persons. Physical and material damages are included in the conception of damage. The meaning of a launching includes any test launch and launch for a real arrangement which will ultimately provides a wide range of compensation. Article 4 indicates that absolute liability should be imposed in compensating for damage by space accidents. Article 4 also indicates that a launching party should be absolutely liable to compensate for the damage caused by its space object on the surface of the Earth. In general, liability stands where fault is. But if the activity is ultra-hazardous and causes serious harm, the individual needs to compensate for the damage unlimitedly. Because of the many launchings for the Seattleite launching, a launching organization is obligated to the liability insurance in preparation for the space accidents. According to the Article 6 of Space Accident Liability Act, to be insured for the compensation for damage is obligatory. It says: "In accordance with Article 11 in the Space Exploration Promotion Act, the person who wants to receive an approval f3r launching needs to be insured in compensation for the possible damage by space accidents.

• The Korean Journal of Physiology
• /
• v.16 no.1
• /
• pp.13-23
• /
• 1982

Effects of external pH and potassium concentrations on the electrical and mechanical properties were investigated on rabbit papillary muscle. Papillary muscles were perfused in horizontal chamber with Tris Tyrode solutions and action potential along with isometric tension was recorded simultaneously. Potassium concentrations were varied between 1 and 12 mM at low(6.9), normal(7.4) and high (7.9) external pH. The following results were obtained: 1) On rasing the potassium concentration from 1 to 12 mM resting membrane potentials decreased from $-88.8{\pm}2.8$ to $-66.4{\pm}1.2\;mV$ at normal pH and the amplitude of action potential decreased from $115.1{\pm}0.7$ to $97.5{\pm}2.8\;mV$. On lowering the potassium concentration, membrane hyperpolarized and at 1 mM potassium concentration resting potentials were $-107{\pm}2.2\;mV$. Duration of action potential especially $APD_{60}{\sim}APD_{90}$ increased($APD_{90}$: $214{\pm}15.8\;ms$ at 1 mM $K^+$ to $287{\pm}18.1\;ms$ at 12 mM $K^+$). 2) During acidosis membranes hyperpolarized by more than 20 mV within 1 min. and then slow recovery was observed during the following 10 min. During alkalosis membranes depolarized about 10 mV, which were maintained until washing with normal Tyrode solutions. 3) On lowering the external pH(7.9-6.5), duration of action potential increased progressively and it was most prominent at pH 6.5 and $K^+$ 1mM. 4) Magnitude of developed tension was $0.6{\pm}0.14\;g/mm^2$ at normal pH and potassium concentration (stimulus frequency : 60/min). Relative isometric tension to normal value increased along the increment of stimulus frequency($44.2{\pm}4.2%$ at 6/min to $271{\pm}86.7%$ at 180/min). Force-frequency relations were altered quantitatively during the perfusion with different external pH solutions. 5) Developed tension did not show marked variation within the range of $2{\sim}8\;mM$ potassium concentrations. Positive inotropism was observed at less than 2 mM $K^+$ and negative inotropism beyond 12 mM $K^+$ concentrations. From the above results we concluded that the effects of potassium ion concentration on electrical and mechanical properties of rabbit papillary muscle are related to the changes in surface negative charge due to acid base disturbances.

• Journal of Sensor Science and Technology
• /
• v.8 no.3
• /
• pp.239-246
• /
• 1999

A highly sensitive photovoltaic infrared photodiode was fabricated for detecting infrared light in $3{\sim}5\;{\mu}m$ wavelength range on InSb wafer with p-i-n structure grown by MOCVD. Silicon dioxide($SiO_2$) insulating films for the junction interface and surface of photodiode were prepared using RPCVD because InSb has low melting point and evaporation temperature. After formation of In ohmic contacts by thermal evaporation, the electrical properties of the photodiode were characterized in dark state at 77K. A product of zero-bias resistance and area($R_0A$) showed $1.56{\times}10^6\;{\Omega}{\cdot}cm^2$ that satisfied BLIP(background limited infrared photodetector) condition. When the photodiode was tested under infrared light, the normalized detectivity of about $10^{11}\;cm{\cdot}Hz^{1/2}{\cdot}W^{-1}$ was obtained. we successfully fabricated a unit cell with InSb IR array with good quantum efficiency and high detectivity.

• Proceedings of the Korean Society of Dyers and Finishers Conference
• /
• 2010.03a
• /
• pp.40-40
• /
• 2010

Studies on attractive color changing property of dye chromophore and fluorophore have been greatly enjoyed in the related industrial and research fields such as optoelectronics, chemosensor, biosensor and so on. The optical property based on D-$\Pi$-A intramolecular charge transfer (ICT) system of chromophore molecules can be utilized as suitable sensing probes for checking media polarity and determining colorimetric chemosensing effect, especially heavy metal detection. These finding are obtained by absorption and emission properties. In this work, donor-acceptor D-$\Pi$-A type fluorescent dyes were designed and synthesized with the corresponding donor and acceptor groups. The selected donor moieties might be provided prominent amorphous properties which are very useful in designing and synthesizing functional polymers and in fabricating devices. Another reasons to choose are commercial availabilities in high purity and low price. Donor-bridge-acceptor (D-A) type dyes can produce impressive optical-physical properties, yielding them potentially suitable for applications in the synthesis of small functional organic molecules. Small organic functional molecules have unique advantages, such as better solubility, amorphous character, and represent an area of research which needs to be explored and developed. Currently, their applications in metalorganic compounds is rapidly expanding and becoming widespread in self-assembly processes, photoluminescence applications, chiral organocatalysts, and ingrafts with nanomaterials. Colloidal nanoparticles have received great attentions in recent years. The photophysical properties of nanoparticles, particularly in terms of brightness, photostability, emission color purity and broad adsorption range, are very attractive functions in many applications. To our knowledge background, colloidal nanoparticles have been enjoyed their applications in bio-probe research fields. This research interest can be raised by the advantages of the materials such as high photoluminescence quantum yields, sharp emission band, long-term photostability and broad excitation spectra. In recent, the uses of nanoparticles being embedded in a polymer matrix and binded on polymer surface have been explored and their properties such as photo-activation and strong photoluminescence have been proposed. The prepared chromophores and nanoparticles were investigated with absorption and emission properties, solvatochromic behaviors, pH induced color switching effects, chemosensing effects and HOMO/LUMO energy potentials with computer simulation. In addition, synthesized fluorophore dyes and particles were applied onto PE/Aramid fiber fluorescing colorations. And the related details were then discussed.

• Economic and Environmental Geology
• /
• v.43 no.6
• /
• pp.573-587
• /
• 2010

Bioleaching experiments were effectively carried out at $42^{\circ}C$, $52^{\circ}C$ and $62^{\circ}C$ to leach the more valuable metal ions from sphalerite using bacteria. The pH values of the bioleaching solution were constantly maintained for 10 days in the range of 2.40 to 2.55. In these bioleaching experiments, rod-shaped bacteria attached to the sphalerite surface were continuously observed in the sample. Along with the increase in the leaching temperatures, the concentration of Zn and Pb increased in the control sample of leachates, whereas the concentration of Fe increased in the sample containing bacteria. At $42^{\circ}C$, $52^{\circ}C$ and $62^{\circ}C$ the biological leaching content of Zn was found to be 9.5, 2.8 and 2.9 times higher than that in the chemical leaching content, respectively. At these temperatures, the content of Pb in the bacterial sample of the leachate was detected to be 14.8, 7.4 and 3.8 times higher than that of the control sample of the leachate, respectively.

• Analytical Science and Technology
• /
• v.18 no.6
• /
• pp.511-519
• /
• 2005

A method for determination of toluene diisocyanates (TDI) in toluene diisocynate (TDI)-based polyurethane (PUR) packing material was investigated, and also the migration of TDI to food was studied. TDI was extracted using food simulants such as n-haptane and 4% aqueous acetic acid. The determinations were performed using gas chromatography/mass spectrometry (GC/MS). One of major components for polyurethane, toluene diisocyanates, were detected in ten samples among twenty six food contact materials with the concentration range of $0.51{\sim}60.88{\mu}g/ml$. However the highest extracted amount was just 0.7% of $60.88{\mu}g/ml$ if the contact surface of food packing for extracting liquid was limited to the outer layer without exposure of the cutting edge of food packing multi-layers. The result of this study and the analysis method for TDI diisocyanate will be very useful for further study about food contact material, and the monitoring result could be used for evaluating the safety of food contact material before it is to be used for food, preservation.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.9
• /
• pp.6221-6226
• /
• 2015

In this paper, waveguide analysis was interpreted as an optical waveguide using the feedback perturbation method simple and easy to apply compared to the analysis method, while the other almost identical to the numerical calculation method. In addition, efficient coupling with an optical transmission line of optical fiber and the waveguide form the thin film of different functional elements is required in order to achieve the full optical communication system. However, problems arise, such as the light field (field) and the decrease of the access efficiency due to inconsistency in the distribution characteristics of the connection surface by the difference in size of the cross section thereof when connecting the optical fiber and the waveguide directly to the combination of a thin film. Therefore propose a new type of connector structure to increase the efficiency of the connection when connecting the optical fiber waveguide and the thin film was analyzed by applying a coupled mode theory, the binding efficiency of the modified contactor. And by diffusing Ti on the $LiNbO_3$ substrate and a wide range of applications in the manufacture of integrated optical material made of a current low-loss Ti: $LiNbO_3$ optical waveguide and making the Y-branch waveguide, and the properties were confirmed.