• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.23 no.7
• /
• pp.1659-1666
• /
• 1998

The multicode CDMA systems that are widely studied as an effective transmission methodology in the IMT-2000 systems, employ orthogonal codes to transform high rate data into parallel, low rate data for simultaneous transmission. In this paper, we propose a new multicode CDMA system which achieves the same data rate and processing gain of the conventional systems, while significantly improves bit error rate performance by exploiting a convolutional code with code rate r=1/2 and a bi-orthogonal code. The simulation results for synchronous systems using maximal ratio combining Rake receivers under additive white Gaussian noise and multi-path fading channels, show significant improviements by the proposed system.

• Membrane Journal
• /
• v.5 no.3
• /
• pp.97-108
• /
• 1995

화학산업의 급속한 성장으로 인해 많은 혜택을 얻고 있지만 반대급부적으로 배출되는 오염물질로 인한 환경오염과 석유 및 석탄과 같은 한정된 화석연료 자원의 과다한 사용이 큰 문제가 되고 있다. 그에 따라 최근에는 효율적인 에너지 활용과 함께 오염물질의 배출을 최대로 억제할 수 있는 경제적이고 션택적인 화학공정을 필요로 하고 있다. 현재 세계적인 기술의 흐름은 대기오염의 억제와 소량 배출되는 오염물질의 제거를 위해 촉매 및 흡착제를 사용하여 다량의 오염물질 또는 기체를 처리할 수 있는 공정의 개발 및 변형에 많은 노력을 기울이고 있다. 그러나 보다 바람직하게는 높은 전환율과 선택적인 화학공정의 도입으로 에너지 효율을 증대시켜 에너지를 절약하고 부산물이 적은 보다 청결한 화학공정으로의 전화을 필요로 하고 있다. 이러한 목적을 위해 무리막의 분리능력과 촉매의 활성을 결합하여 촉매반응과 반응물 및 생성물의 분리기능을 동시에 수행할 수 있는 무기막 촉매기술이 최근들어 광범위하게 연구되고 있다. 또한 최근에는 무기막 및 무기막 촉매의 환경분야에의 이용이 크게 확산되어 가고 있는 추세이기 때문에 막 및 막 촉매 기술은 중요성이 매우 높은 분야이다. 따라서 본 고찰에서는 최근에 연구가 활발히 진행되고 있는 무기막 촉매기술의 특성과 연구 현황 및 방향에 관해 살펴보고 향후 연구방향의 기초자료로서 활용하고자 한다.

• Journal of the Korean Applied Science and Technology
• /
• v.33 no.4
• /
• pp.795-801
• /
• 2016

This study is on the denitrification process using the sodium alginate and $CaCl_2$ as a flocculant. Removal techniques of nitrate nitrogen from waste water are reverse osmosis, ion exchange, electro dialysis and biological method etc. We tried to remove nitrate nitrogen with flocculation and sedimentation method in the present study. Calcium alginate is expected to form a chelate bond with nitrate nitrogen in the solution. So the effects of flocculantt component, flocculation reaction time, molar ratio of the flocculant, flocculant injection rate are studied to determine the best removal rate of nitrate nitrogen. In addition, we tried to determine the nitrate nitrogen removal mechanism by analyzing the structure and component ratio of the configuration after the agglutination precipitate by FE-SEM and EDS. As a result, the nitrate nitrogen removal mechanism is turned out to form calcium-nitro-alginate, and the best mole ratio of flocculating agent is 1 : 1, the injection rate of the flocculant was up to 2%, the removal rate of the nitrate nitrogen to be 56.7% in the synthetic wastewater.

• Korean Chemical Engineering Research
• /
• v.55 no.6
• /
• pp.837-845
• /
• 2017

A recirculating integrated system composed of a fluidized biofilter filled with waste-tire crumb media fixed with return sludge from wastewater treatment facility of D dyeing industrial center, and a UV/photocatalytic reactor packed with calcined $TiO_2$ coated-glass beads as photocatalyst-support, was constructed and was run to treat authentic textile-dyeing wastewater from D-dyeing industrial center, which was mixed with an alkaline polyester-weight-reducing wastewater and a wastewater from sizing process. As a result, its total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were ca. 81% and 55%, respectively. The synergy effect of the recirculating integrated system to enhance total removal efficiency(RE(tot)) of $COD_{cr}$ and colors were evaluated at most ca. 7% and 3%, respectively. The fluidized biofilter and the UV/photocatalytic reactor were responsible for ca. 94% and 6% of the total $COD_{cr}$ removal efficiency, respectively, and were also responsible for ca. 86% and 14% of the total color-removal efficiency, respectively. Thus, the degree of the UV/photocatalytic reactor-unit process's contribution to RE(tot) of color, was about 2.4 times of that to RE(tot) of $COD_{cr}$. Therefore, the UV/photocatalytic reactor facilitated the more effective elimination of colors by breaking down the chemical bonds oriented from colors of dyes such as azo-bond, than $COD_{cr}$. In addition, the effect of the removal efficiency of each unit process(i.e., the fluidized biofilter or the UV/photocatalytic reactor) of the recirculating integrated system on RE(tot) of $COD_{cr}$ and colors, was analysed by establishing its model equation with an analytic correlation.

• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.5
• /
• pp.519-524
• /
• 2005

Due to the low C/N ratio of domestic wastewater characteristic, addition of external carbon source for the effective N and P removal is necessary. High organic content of food waste can be used for the external carbon source in biological nutrient removal processes, The applicability of condensate of food waste (CFW), which is produced during the high-rate fermentation process, was examined in membrane bioreactor for the nutrient removal. Under the various operating conditions, nutrient removal efficiencies and membrane fouling characteristics were evaluated using synthetic wastewater. From nitrate utilization rate (NUR) test, denitrification rate was 0.19 g $NO_3-N/g$ VSS/day. With the addition of CFW increased, average removal efficiencies of T-N and T-P could be increased up to 64% and 41%, respectively. Also the optimal retention time was 3 hr/5 hr for anoxic/aerobic reactor. When applied to real sewage, membrane fouling resistance was increased up to 60%, which could be reduced from $10.4{\times}10^{12}m^{-1}$ to $5.9{\times}10^{12}m^{-1}$ with the control of influent suspended solid concentration. In summary, it was suggested that CFW could be used as an economical and effective carbon source for membrane assisted biological N and P removal.

• Journal of Digital Convergence
• /
• v.14 no.10
• /
• pp.261-269
• /
• 2016

This paper aims to propose a novel technology of network convergence to provide ultra high speed internet services over CATV networks, by which a CMC(cable modem concentrator) and CM(cable modem) of 1Gbps level are designed. This technology not only lowers the production cost in comparison to the existing bonding technology with DOCSIS specification but also enables the adjustment of data speed based on the channel bandwidth. According to the experiments, when convolutional code rate with 128QAM is changed to 1/2, 2/3, 3/4 and 7/8, the data recorded the maximum transmission speed of up to 299 Mbps at the zero error rate. As the convolutional code rates with 256QAM is increased, it showed 334Mbps at the error rate of $10^{-5}$. Based on the findings of this paper, if we secure the channel bandwidth of 200MHz and adjust the modulation order of QAM and the convolution code rate depending on the channel status, we can get the transmission speed of more than 1Gbps, which is much more competitive in its function and price than the existing technology based on DOCSIS.

• Applied Chemistry for Engineering
• /
• v.26 no.1
• /
• pp.104-110
• /
• 2015

It is known that polymer concretes are 8~10 times more expensive than ordinary Portland cement concretes; therefore, in the production of polymer concrete products, it is very important to reduce the amount of polymer binders used because this occupies the most of the production cost of polymer concretes. In order to develop a technology for the reduction of polymer binders, smooth and spherical aggregates were prepared by the atomizing technology using the oxidation process steel slag (electric arc furnace slag, EAFS) and the reduction process steel slag (ladle furnace slag, LFS) generated by steel industries. A reduction in the amount of polymer binders used was expected because of an improvement in the workability of polymer concretes as a result of the ball-bearing effect and maximum filling effect in case the polymer concrete was prepared using the smooth and spherical atomized steel slag instead of the calcium carbonate (filler) and river sand (fine aggregate) that were generally used in polymer concretes. To investigate physical properties of the polymer concrete, specimens of the polymer concrete were prepared with various proportions of polymer binder and replacement ratios of the atomized reduction process steel slag. The results showed that the compressive strengths of the specimens increased gradually along with the higher replacement ratios of the atomized steel slag, but the flexural strength showed a different maximum strength depending on the addition ratio of polymer binders. In the hot water resistance test, the compressive strength, flexural strength, bulk density, and average pore diameter decreased; but the total pore volume and porosity increased. It was found that the polymer concrete developed in this study was able to have a 19% reduction in the amount of polymer binders compared with that of the conventional product because of the remarkable improvement in the workability of polymer concretes using the spherical atomized oxidation steel slag and atomized reduction steel slag instead of the calcium carbonate and river sand.

• Journal of the Korea Concrete Institute
• /
• v.27 no.2
• /
• pp.127-136
• /
• 2015

To evaluate the effects of limestone powder and silica fume on the properties of high-strength high-volume ground granulated blast-furnace slag (GGBFS) blended cement concrete, this study investigated the rheology, strength development, hydration and pozzolanic reaction characteristics, porosity and pore size distribution of high-strength mortars with the water-to-binder ratio of 20, 50 to 80% GGBFS, up to 20% limestone powder, and up to 10% silica fume. According to test results, compared with the Portland cement mixture, the high-volume GGBFS mixture had much higher flow due to the low surface friction of GGBFS particles and higher strength in the early age due to the accelerated cement hydration by increase of free water; however, because of too low water-to-binder ratio and cement content, and lack of calcium hydroxide content, the pozzolanic reactio cannot be activated and the long-term strength development was limited. Limestone powder did not affect the flowability, and also accelerate the early cement hydration. However, because its effect on the acceleration of cement hydration is not greater than that of GGBFS, and it does not have hydraulic reactivity unlikely to GGBFS, compressive strength was reduced proportional to the replacement ratio of limestone powder. Also, silica fume and very fine GGBFS lowered flow and strength by absorbing more free water required for cement hydration. Capillary porosities of GGBFS blended mortars were smaller than that of OPC mortar, but the effect of limestone powder on porosity was not noticeable, and silica fume increased porosity due to low degree of hydration. Nevertheless, it is confirmed that the addition of GGBFS and silica fume increases fine pores.

• 전기의세계
• /
• v.24 no.4
• /
• pp.6-10
• /
• 1975

반도체와 그의 응용소자는 지난 20여년간 눈부식 발전을 이룩하였다. 이는 주로 단결정의 제작기술 진보에 의한 것으로 본다. 그러나 최근 단결정과는 전연 다른 유리질반도체가 국제회의에서도 그 우수성을 의논하기에 이르렀다. 유리질 반도체가 주목을 끌게 된겻은 1968년 Ovshinsky가 "무질서 구조에 있어서 가역적 스위칭현상"이라는 논문이 발표되고 유리질 반도체를 사용한 Ovonic 스위칭 소자의 출현에 기인된다. 유리질 반도체가 전기스위칭 작용, 기억작용을 나타낸다고 하는 Ovshinsky의 발표는 전자제치로서의 응용에 대해 찬반되는 의견이 있었지만 물성적 연구의 교량적인 역할을했다고 할 수 있다. 이런 반도체에 속하는 재료는 호칭도 여러가지로 유리질반도체, 비정질반도체 무정형반도체등으로 불리어진다. 단결정체가 각 격자간에 장거리질서를 갖는 반면 유리질 반도체는 무질서한 구조로 각 격자간에 단거리 질서를 갖는 것이 단결정과는 본질적으로 다른 점이라 본다. 유리 반도체의 종류는 첫째, 원소성 유리반도체로서 Ge, Si, Se, Te 들과 같이 단일원소로 된 겻과, 둘째 IV, V, VI족 원소로 된 공유결합 합금인 As$_{2}$Se$_{3}$-As$_{2}$Te$_{3}$ 계 Ge Si As Te계등의 칼코게나이드 유리등으로 금지대는 어느 것이나 2eV이하이다. 셋째 이론결합인 SiO $Al_{2}$O$_{3}$ Ta$_{2}$O$_{3}$Si$_{3}$N$_{4}$등의 산화물 및 질화물로 대표되는 분자성 비정질 물질로서 금지대는 2eV보다 큰 세종류로 크게 분류할 수 있다. 분류할 수 있다. 한다. 단 개개의 문제에 관한 구체적인 해석 또는 검토에 관하여는 다음 기회에 미루기로하고, 우선 여기서는 당면문제로서 대처하지 않으면 안될 자동주파수제어문제및 계통의 경제운용문제만에 한정하여, 이것을 우리나라의 현상과 관련시켜 개설하고, 이들의 자동화에 관한 기본적인 문제를 간단히 적어 보겠다. 가능하다. 제작완료된 ASIC은 기능시험을 완료했으며 실제 line-of-sight(LOS) 시스템 구현에 적용중이다. 시대를 살아 갈 회원들이다. '컨텐츠의 시대'가 개막되는 것이며, 신세기통신과 SK텔레콤은 선의의 경쟁 과 협력을 통해 이동인터넷 서비스의 컨텐츠를 개발해 나가게 될 것이다. 3배가 높았다. 효소 활성에 필수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의 회수 및 재사용이 가능하게 해준다.해준다.다. TN5 세포주를 0.2 L 규모 (1 L spinner flask)oJl에서 세포간의 응집현상 없이 부유배양에 적응,배양시킨 후 세포성장 시기에 따른 발현을 조사한 결과 1 MOI의 감염조건 하에서는 $0.6\times10^6$cell/mL의 early exponential시기의 세포밀도에서 72시간 배양하였을 대 최대 발현양을

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.25 no.11
• /
• pp.1128-1134
• /
• 2014

In this paper, the effects of a metamaterial slab with negative permeability in a magnetically coupled wireless power transfer system (WPT) in the overall performance are analyzed quantitatively in terms of the effective quality factors of the loop resonators and coupling coefficient considering the slab losses, based on an equivalent circuit. Using the ideal metamaterial slab(lossless slab), the WPT efficiency is improved considerably by the magnetic flux focusing. However, the practical lossy slab made of RRs or SRRs limits the significant enhancement of WPT efficiency due to the relatively high losses in the slab consisting of RRs or SRRs near the resonant frequency. For the practical loop resonator, other than a point magnetic charge, using the practical lossy metamaterial slab in order to improve the transfer efficiency, the width of the slab needs to be optimized somewhat less than the half of the distance between two loop resonators. For the low-loss slab with its loss tangent of 0.001, the WPT efficiency is maximized at 93 % when the ratio of the slab width and the distance between the two resonators is approximately 0.35, compared with 53 % for the case without the slab. The efficiency in case of employing the high-low slab(loss tangent: 0.2) is maximized at 61 % when the slab ratio is 0.25.