• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2005년도 추계종합학술대회
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• pp.201-204
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• 2005

In this paper, based on an extended model containing correlator and soft decision decoding, the capacity is evaluated in the single-user case when the inputs are equiprobable. With this method, we adjusted optical communication over AWGN. It is found that only when bit- signal-to-noise ratio (bit-SNR) is high enough, larger M leads to higher capacity; and for a specific M, the optimal values of PPM time offset parameter Td, which maximize the capacity, are independent of bit-SNR. In this paper, the capacity of UWB system in optical fiber over AWGN is proven to improve 1.73 times larger than AWGN channel Capacity.

• 한국통신학회논문지
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• 제33권4A호
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• pp.361-370
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• 2008

Cooperative relaying permits one or more relay to transmit a signal from the source to the destination, thereby increasing network coverage and spectral efficiency. The performance of cooperative relaying is often measured as outage probability. However, appropriate measure for the channel quality is outage capacity. Although the outage probability for cooperative relaying protocol has been analyzed before, very little research has been addressed for the outage capacity. This paper is the first of its kind to derive a closed-form analytical solution of outage capacity using fixed decode and forward relaying and amplify and forward relaying in dissimilar Rayleigh fading channels, considering channel coefficients known to the receiver side. The analytical results show a tradeoff between the SNR and the number of relays for specific outage capacity. A comparison between decode and forward relaying and amplify and forward relaying shows that decode and forward relaying outperforms amplify and forward relaying for a large number of relays.

• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1988-1992
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• 2010

4-Amino-1,2,4-triazole copper complex (4-ATzCu) was synthesized, and its thermal behaviors, nonisothermal decomposition reaction kinetics were studied by DSC and TG-DTG techniques. The thermal decomposition reaction kinetic equation was obtained as: $d\alpha$ / dt =$10^{22.01}$ (1-$\alpha$)[-ln(1-$\alpha$)]$^{1/3}$ exp($-2.75\times10^4$ /T). The standard mole specific heat capacity of the complex was determined and the standard molar heat capacity is 305.66 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ at 298.15 K. The entropy of activation $({\Delta}S^{\neq})$, enthalpy of activation $({\Delta}H^{\neq})$, and Gibbs free energy of activation $({\Delta}G^{\neq})$ are calculated as 171.88 $J{\cdot}mol^{-1}{\cdot}K^{-1}$ 225.81 $kJ{\cdot}mol^{-1}$ and 141.18 $kJ{\cdot}mol^{-1}$, and the adiabatic time-to-explosion of the complex was obtained as 389.20 s.

• 전기화학회지
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• 제2권2호
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• pp.61-65
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• 1999

리튬이차전지용 양극물질로서 $LiV_3O_8$의 새로운 합성방법이 그 전기화학적 거동을 향상시키는 것으로 제안되고 있다. $LiV_3O_8$을 수용성 lithium trivanadate 겔의 탈수에 의해 잘 분산된 형태로 얻어진다. $LiV_3O_8$의 초음파처리방법은 solutionmethod에 의해 만들어진 초기상태의 $LiV_3O_8$과 비교된다. 수용액상에서 초음파처리 된 물질은 XRD, TGA, SEM등으로 물리적특성을 확인하였다. 이런 방법들은 수용성 $LiV_3O_8$의 초음파처리공정이 결정성을 감소시키고 비표면적과 공간용량을 향상시키는 것으로 나타났다. 특히 2시간 동안 초음파처리한 것은 높은 방전용량을 가지며, 대용량의 손실없이 충방전사이클이 이루어졌다. 따라서, 초음파처리 된 $LiV_3O_8$은 공간용량을 향상시킬 뿐만 아니라 사이클거동 역시 향상되었다.

• 대한교통학회지
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• 제1권1호
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• pp.56-63
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• 1983

Intersection control has dual-purposes; increasing capacity and reducing delay. The primary concern of efficient intersection control under oversaturated condition as in Korea is to increase capacity. Prevailing intersection operation technique permits thru traffic to utilize left turn lane, because the intersection without left turn pocket has left turn signal interval. In this situation, it seems not to be valid to calculate capacity, delay, and signal timings by conventional methods. By critical lane technique, capacity increases as cycle length increases. However, when thru traffic utilize LT lane, the capacity varies according to LT volume, LT interval as well as cycle length, which implies that specific cycle length and LT interval exist to maximize capacity for given LT volume. The study is designed is designed to calculate utilization factors of LT lane for thru traffic and capacities, and identify signal timings to yield maximum capacity. The experimental design involved has 3 variables; 1)LT volumes at each approach(20-300 vph), 2)cycle lengths (60-220 sec), and 3)LT intervals(2.6-42 sec) for one scenario of isolated intersection crossing two 6-lanes streets. For LT volume of 50-150 vph, capacity calculated by using the utilization factor is about 25% higher than that by critical lane method. The range of optimum cycle length to yield maximum capapcity for LT volume less than 120 vph is 140-180 sec, and increases as LT volume increases. The optimum LT interval to yield maximum capacity is longer than the intrval necessary to accommodate LT volume at saturation flow rate.

• 한국지하수토양환경학회지:지하수토양환경
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• 제19권2호
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• pp.25-37
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• 2014

The volcanic type of geothermal water is linked intimately to active or potentially active volcanoes and takes place near the plate boundaries. In contrast to the volcanic type, the geothermal water in Korea has a non-volcanic origin. Korea's geothermal water is classified into the residual magma (RM) type and deep groundwater (DG) type according to the criterion of $35^{\circ}C$. This study reviewed the relationship between the physical and chemical features of the 281 geothermal water sources in South Korea in terms of the specific capacity, water temperature, and chemical compositions of two different basements (igneous rock and metamorphic rock) as well as the geological structures. According to the spatial relationship between the geothermal holes and geological faults, the length of the major fault is considered a key parameter determining the movement to a deeper place and the temperature of geothermal water. A negligible relationship between the specific capacity (Q/s) and temperature was found for both the RM type and DG type with the greater specific capacities of the RM- and DG-igneous types than the RM- and DG-metamorphic types. No relationship was observed between Q/s and the chemical constituents ($K^+$, $Na^+$, $Ca^{2+}$, $Mg^{2+}$, $Zn^{2+}$, $Cl^-$, $SO_4{^{2-}}$, $HCO_3{^-}$, and $SiO_2$) in the DG-igneous and DG-metamorphic types. Furthermore, weak relationship between temperature and chemical constituents was found for both the RM type and DG type.

• 한국초전도ㆍ저온공학회논문지
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• 제21권1호
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• pp.40-44
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• 2019

This study investigates mixtures of water and cryoprotectant agents (CPAs) to store high-grade cold energy. Although water is an ideal material for a cold thermal storage (CTS) due to its high specific heat, undesirable volume expansion may cause structural stresses during freezing. The volume expansion can be alleviated by adding the CPAs to water. However, the CPA aqueous solutions not only have different thermal properties but also transit to amorphous state different from pure water. Therefore, these characteristics should be considered when using them as material of the CTS. In experiments, glycerol and dimethyl sulfoxide (DMSO) are selected as the candidate CPA. The volume expansion of the solution is measured by an in-situ strain gauge in low temperature region. The specific heat capacity of the solution is also measured by differential scanning calorimetry (DSC). Both the amount of volume expansion and the specific heat capacity of the CPA aqueous solution decrease in the case of higher concentration of CPA. These characteristics should be contemplated to select optimal aqueous solution for CTS for liquid air energy storage system (LAES). The CPA solutions have advantages of having wide temperature range to utilize the latent heat of water and higher sensible heat of the CPA. The CPA solutions which can satisfy the allowable stress of the structure are determined. Consequently, among the CPA solutions investigated, DMSO 20% w/w solution is the most suitable for the CTS.

• 한국전기전자재료학회논문지
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• 제19권1호
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• pp.64-70
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• 2006

In this study, the $LiCoO_2/LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ mixed cathode electrodes were prepared and their electrochemical performances were measured in a high cut-off voltage. As the content of $LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ increased in a mixed cathode, the reversible specific capacity and cycleability of the electrode enhanced, but the rate capability was deteriorated. On the contrary the rate capability of the cathode enhanced, but the reversible specific capacity and cycleability were deteriorated, increasing the content of $LiCoO_2$ in the mixed cathode. The cell of $LiCoO_2/LiNi_{1/3}Mn_{1/3}Co_{1/3}O_2$ ($50:50 wt\%$) mixed cathode delivered a discharge capacity of ca. 168 mAh/g at a 0.2 C rate. The capacity of the cell decreased with the current rate and a useful capacity of ca. 152 mAh/g was obtained at a 2.0 C rate. However, the cell showed very stable cycleability: the discharge capacity of the cell after 20th charge/discharge cycling maintains ca. 163 mAh/g.

• 한국주조공학회지
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• 제25권2호
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• pp.73-79
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• 2005

Effects of Cr and Ni addition on damping capacity, mechanical property, and corrosion resistance of Fe-17%Mn martensitic alloy have been studied. Martensite start temperature($M_{S}$) of the alloy decreases linearly with increasing Cr and Ni contents up to 15%. The damping capacity decreases gradually from 27 to 22% in specific damping capacity(SDC) with increasing Cr and Ni contents from zero to 10%, and decreases rapidly with further Cr and Ni content in Fe-17%Mn alloy. The tensile strength of the alloy maintains a level of 60 $kgf/mm^{2}$ regardless of Cr content with an elongation of 20 to 25%. But, in case of Fe-17%Mn-x%Ni alloy, the tensile strength decreased rapidly with the Ni content of above 10% because of austenite morphology. Immersion test in 5% NaCl solution leads to the result that the corrosion resistance of the alloy becomes excellent above 10% Cr. From the above results, it is concluded that the optimum Cr content to improve the mechanical property and corrosion resistance of the alloy in 5%NaCl solution with a lesser decrease in damping capacity is about 10%. In the case of 5% $H_{2}SO_{4}$ condition, the Fe-17%Mn-10%Ni is an optimum alloy.

• Advances in materials Research
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• 제8권1호
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• pp.37-46
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• 2019

Electrochemical double layer capacitors (EDLCs) which are fabricated using carbon based electrodes have been emerging at an alarming rate to fulfill the energy demand in the present day world. Activated charcoal has been accepted as a very suitable candidate for electrodes but its cost is higher than natural graphite. Present study is about fabrication of EDLCs using composite electrodes with activated charcoal and Sri Lankan natural graphite as well as a gel polymer electrolyte which is identified as a suitable substitute for liquid electrolytes. Electrochemical Impedance Spectroscopy, Cyclic Voltammetry and Galvanostatic Charge Discharge test were done to evaluate the performance of the fabricated EDLCs. Amount of activated charcoal and natural graphite plays a noticeable role on the capacity. 50 graphite : 40 AC : 10 PVdF showed the optimum single electrode specific capacity value of 15 F/g. Capacity is determined by the cycling rate as well as the potential window within which cycling is being done. Continuous cycling resulted an average single electrode specific capacity variation of 48 F/g - 16 F/g. Capacity fading was higher at the beginning. Later, it dropped noticeably. Initial discharge capacity drop under Galvanostatic Charge Discharge test was slightly fast but reached near stable upon continuous charge discharge process. It can be concluded that initially some agitation is required to reach the maturity. However, the results can be considered as encouraging to initiate studies on EDLCs using Sri Lankan natural graphite.