• Journal of KIISE:Information Networking
• /
• v.31 no.2
• /
• pp.196-206
• /
• 2004

In the Next Generation Internet(NGI) backbone network, a Dense Wavelength Division Multiplexing (DWDM) technology has been more and more highlighted to cover the increasing subscribers and bandwidth requirement. For such a DWDM network, Routine and Wavelength Assignment (RWA) is the essential problem to establish the optimal path and assign a wavelength efficiently to the selected path in resource utilization. However, the existing RWA algorithms do not consider the congestion in the network so that the performance of then is so limited. To solve this problem, in this paper, we introduce a new RWA algorithm, called Multi Wavelength-Minimum Interference path Routing (MW-MIPR) that establishes a routing path to minimize the interference for many potential future connection setup request. And then, we also propose a wavelength-routed QoS routing scheme based on differentiated QoS classes with applying MW-MIPR algorithm. Simulation results are also given to prove the efficiency of the proposed algorithms.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.40 no.8
• /
• pp.1606-1612
• /
• 2015

In this paper, a portable high efficiency nondispersive infrared(NDIR) $CO_2$ sensor module with a smart device interface is developed. For low power consumption design, an IR LED was used instead of tungsten lamp for light source and an optical waveguide optimized to the sensor module is designed. With the smart device interface, power of the sensor module is applied from the battery of smart phone. The measured data of the sensor module such as $CO_2$ concentration, temperature, and humidity are displayed on the smart phone using android application. From measured results, the developed sensor module shows ${\pm}60ppm$ tolerance error from 0 to 3,000ppm $CO_2$ concentration range among $-10^{\circ}C$ and $50^{\circ}C$ ranges.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2009.04a
• /
• pp.23-28
• /
• 2009

The purpose of this study was to improve not only wet-end performances but also paper characteristics by the modification of various factors like molecular design and ionic characteristics of polyacrylamides First of all physical characteristics were observed after modify molecular design of the cationic polyacrylamides to linear, branched and cross-linked. In addition it was found analysis method to confirm branch degree of cationic polyacrylamides to combine ionic titration characteristics and spectroscopic behavior, After application of these structure modified polyacrylamides to the multiple retention systems with inorganic microparticles, it was found adjusting of branch degree of polyacrylamides was very important to optimize wet-end improvement. Second, After polymerization of amphoteric polyacrylamide to have both of cationic and anionic functional group in the polymer, we observed not only physical characteristics but also wet-end improvement to apply recycled pulp and found that the improvement of solution stability to prevent hydrolysis and increase of ash retention dramatically to compare traditional cationic polyacrylamide retention aid, Finally, After polymerization of anionic polyacrylamide, we observed not only wet-end improvement but also paper characteristics to apply preflocculation of PCC and it was found the improvements of flocculation efficiency, retention, ash retention, optical properties of the paper and bursting strength to compare traditional preflocculant of cationic polyacrylamide.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.157-157
• /
• 2010

Vertical-structure light-emitting diodes (V-LEDs) by laser lift-off (LLO) have been exploited for high-efficiency GaN-based LEDs of solid-state lightings. In V-LEDs, emitted light from active regions is reflected-up from reflective ohmic contacts on p-GaN. Therefore, silver (Ag) is very suitable for reflective contacts due to its high reflectance (>95%) and surface plasmon coupling to visible light emissions. In addition, low contact resistivity has been obtained from Ag-based ohmic contacts annealed in oxygen ambient. However, annealing in oxygen ambient causes Ag to be oxidized and/or agglomerated, leading to degradation in both electrical and optical properties. Therefore, preventing Ag from oxidation and/or agglomeration is a key aspect for high-performance V-LEDs. In this work, we demonstrate the enhanced thermal stability of Ag-based Ohmic contact to p-GaN by reducing the thermal compressive stress. The thermal compressive stress due to the large difference in CTE between GaN ($5.6{\times}10^{-6}/^{\circ}C$) and Ag ($18.9{\times}10^{-6}/^{\circ}C$) accelerate the diffusion of Ag atoms, leading to Ag agglomeration. Therefore, by increasing the additional residual tensile stress in Ag film, the thermal compressive stress could be reduced, resulting in the enhancement of Ag agglomeration resistance. We employ the thin Ni layer in Ag film to form Ni/Ag mutli-layer structure, because the lattice constant of NiO ($4.176\;{\AA}$ is larger than that of Ag ($4.086\;{\AA}$). High-resolution symmetric and asymmetric X-ray diffraction was used to measure the in-plane strain of Ag films. Due to the expansion of lattice constant by oxidation of Ni into NiO layer, Ag layer in Ni/Ag multi-layer structure was tensilely strained after annealing. Based on experimental results, it could be concluded that the reduction of thermal compressive stress by additional tensile stress in Ag film plays a critical role to enhance the thermal stability of Ag-based Ohmic contact to p-GaN.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.134-134
• /
• 2012

We investigated the interface of poly (3-hexylthiophene) (P3HT) and C61-butyric acid methylester (PCBM) by using photoelectron spectroscopy (PES). These are the most widely used materials for bulk heterojunction (BHJ) organic solar cells due to their high efficiency. Study of the BHJ interfaces is difficult because the organic films are typically prepared by spin coating in ambient conditions. This is incompatible with the interface electronic structure probes such as PES, which requires ultrahigh vacuum conditions. Study of interface requires gradual deposition of thin films that is also incompatible with the spin coating process. In this work, we used electrospray vacuum deposition (EVD) technique to deposit P3HT and PCBM in high vacuum conditions. EVD allows us to form polymer thin films onto ITO substrate in a step-wise manner directly from solutions and to use PES without exposing the sample to the ambient condition. Although the morphology of the EVD deposited P3HT films observed by optical and atomic force microscopes is quite different from that of the spin coated ones, the valence region spectra were similar. PCBM was deposited on the P3HT film in a similar manner and the energy level alignment between these two materials was studied. We discuss the relation between Voc of P3HT:PCBM solar cell and HOMO-LUMO energy offset obtained in this study.

• Journal of Biosystems Engineering
• /
• v.40 no.3
• /
• pp.271-276
• /
• 2015

Purpose: Quick freezing is widely used in commercial food storage. Well-known freezing techniques such as individual quick freezing require a low-temperature coolant and small cuts for the heat-transfer efficiency. However, the freezing method for bulk food resembles techniques used in the 1970s. In this study, electromagnetic (EM) heating was applied to improve the quick freezing of bulk food. Methods: During freezing, the surface of food can be rapidly cooled by an outside coolant, but the inner parts of the food cool slowly owing to the latent heat from the phase change. EM waves can directly heat the inner parts of food to prevent it from freezing until the outer parts finish their phase change and are cooled rapidly. The center temperature of garlic cloves was probed with optical thermo sensors while liquid nitrogen (LN) was sprayed. Results: When EM heating was applied, the center cooling time of the garlic cloves from freezing until $-10^{\circ}C$ was 48 s, which was approximately half the value of 85 s obtained without EM heating. For the white radish cubes, the center cooling time was also improved, from 288 to 132 s. The samples frozen by LN spray with EM heating had a closer hardness to the unfrozen samples than the samples frozen by LN only. Conclusions: The EM heating during quick freezing functions to maintain the hardness of fresh food by reducing the freezing time from 0 to $-10^{\circ}C$.

• Journal of Korean Society for Atmospheric Environment
• /
• v.22 no.6
• /
• pp.863-875
• /
• 2006

Intensive visibility monitoring was conducted to investigate physical and chemical characteristics of visibility impairment by airborne pollen. Light attenuation coefficients were optically measured by a transmissometer, a nephelometer, and an aethalometer. Elemental, ionic, and carbonaceous species were chemically analyzed on the filters collected by $PM_{2.5}$ and $PM_{10}$ samplers. Aerosol size distribution was analyzed using a cascade impactor during airborne pollen period. Airborne pollen count was calculated using a scanning electron microscope. Airborne pollen was emitted into the atmosphere in springtime and funker degraded visibility through its scattering and absorbing the light. Average light extinction coefficient was measured to be $211{\pm}36Mm^{-1}$ when airborne pollen was not observed. But it increased to $459{\pm}267Mm^{-1}$ during the airborne pollen period due to increase of average $PM_{2.5}$ and $PM_{10}$ mass concentration and relative humidity and airborne pollen count concentration for $PM_{10}$, which were measured to be $46.5{\pm}29.1{\mu}g\;m^{-3},\;97.0{\pm}41.7{\mu}g\;m^{-3},\;54.1{\pm}11.6%$, and $68.2{\pm}89.7m^{-3}$, respectively. Average light extinction efficiencies for $PM_{2.5}$ and $PM_{10}$ were calculated to be $5.9{\pm}0.9$ and $4.5{\pm}0.8m^2 g^{-1}$ during the airborne pollen period. Light extinction efficiency for $PM_{10}$ increased further than that for $PM_{2.5}$. The average light extinction budget by airborne pollen was estimated to be about 24% out of the average measured light extinction coefficient during the airborne pollen period.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.43 no.1
• /
• pp.72-78
• /
• 2015

Recently, the usage of the satellite is increased more and more in the areas that are communication, weather, marine, optical, radar etc. The functions of the Satellite are evolving from passive transponder to active transponder by the developing of a technology. Advanced countries in satellites install the DCAMP for increase of bandwidth efficiency, improvement of QoS by interference rejection. DCAMP includes many digital components in order to implement functions. Thus, these kinds of active transponders consume much more power compared to passive transponder and then increase the heat. In this paper, we discuss the TVAC test result of DCAMP in EQM(Engineering Qualification Model) level. The paper shows the test results of digital gain control in order to verify DCAMP status under the TVAC test. In addition, the temperature and heat condition of main components from viewpoint of derating will be treated through the official environment test for qualification.

• Journal of Information Display
• /
• v.8 no.2
• /
• pp.10-14
• /
• 2007

A blazed $GxL^{TM}$ device is described as having high optical efficiency (> 70% for RGB lasers), and high contrast ratio (> 10,000:1), and that is highly reliable when used in a large-area laser projection system. It has a robust design and precise stress control technology to maintain a uniform shape (bow and tilt) of more than 6,000 ribbons, a $0.25-{\mu}m$ CMOS compatible fabrication processing and planarization techniques to reduce fluctuation of the ribbons, and a reliable Al-Cu reflective film that provided protection against a high-power laser. No degradation in characteristics of the GxL device is observed after operating a 5,000- lumen projector for 2,000 hours and conducting 2,000 temperature cycling tests at $-20^{\circ}C$ and $+80^{\circ}C$. At the 2005 World Exposition in Aichi, Japan the world's largest laser projection screen with a size of 2005 inches (10 m ${\times}$ 50 m) and 6 million pixels (1,080 ${\times}$ 5,760) was demonstrated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.9B
• /
• pp.777-784
• /
• 2006

In this paper, we propose the PON-based access network based on conventional TDM-PON architecture, which utilizes WDM wavelength channel and bandwidth dynamically. It is also described a dynamic MAC protocol in order to increase the number of subscribers and efficiency of resource utilization. Of particular importance in the proposed approach for MAC protocol is that the wavelength channel and time slot for up/downlink is dynamically allocated according to the required QoS level and the amount of data in data transmission, through the dedicated control channel between OLT and ONU. We evaluate the performance of average packet end-to-end delay in a statistical analysis and numerical analysis. In addition, through simulations with various traffic models, we verified the superior performance of the proposed approach by comparing with the results of other E-PONs.