• BMB Reports
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• 제44권1호
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• pp.1-10
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• 2011

Inter-cellular communication via diffusible small molecules is a defining character not only of multicellular forms of life but also of single-celled organisms. A large number of bacterial genes are regulated by the change of chemical milieu mediated by the local population density of its own species or others. The cell density-dependent "autoinducer" molecules regulate the expression of those genes involved in genetic competence, biofilm formation and persistence, virulence, sporulation, bioluminescence, antibiotic production, and many others. Recent innovations in recombinant DNA technology and micro-/nano-fluidics systems render the genetic circuitry responsible for cell-to-cell communication feasible to and malleable via synthetic biological approaches. Here we review the current understanding of the molecular biology of bacterial intercellular communication and the novel experimental protocols and platforms used to investigate this phenomenon. A particular emphasis is given to the genetic regulatory circuits that provide the standard building blocks which constitute the syntax of the biochemical communication network. Thus, this review gives focus to the engineering principles necessary for rewiring bacterial chemo-communication for various applications, ranging from population-level gene expression control to the study of host-pathogen interactions.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.39-42
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• 2002

Recently, CMP (chemical mechanical polishing) technology has been widely used for global planarization of multi-level interconnection for ULSI applications. However, COO (cost of ownership) and COC (cost of consumables) were relatively increased because of expensive slurry. In this paper, we have studied the possibility of recycle of reused silica slurry in order to reduce the costs of CMP slurry. The post-CMP thickness and within-wafer non-uniformity(WIWNU) were measured as a function of different slurry composition. As a experimental result, the performance of reused slurry with annealed silica abrasive of 2 wt% contents was showed high removal rate and low non-uniformity. Therefore, we propose two-step CMP process as follows In the first-step CMP, we can polish the thick and rough film surface using remaked slurry, and then, in the second-step CMP, we can polish the thin film and fine pattern using original slurry. In summary, we can expect the saving of high costs of slurry.

• 대한금속재료학회지
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• 제46권3호
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• pp.144-149
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• 2008

Equal channel angular pressing (ECAP) has been studied intensively over the decade as a typical top-down process to produce ultrafine/nano structured materials. ECAP has successfully been applied for a processing method of severe plastic deformation to achieve grain refinement of magnesium and to enhance its low ductility. However, difficult-to-work materials such as magnesium and titanium alloys were susceptible to shear localization during ECAP, leading to surface cracking. The front pressure, developed by Australian researchers, can impose hydrostatic pressure and increase the strain level in the material, preventing the surface defect on workpiece. In the present study, we investigated the deformation and fracture behavior of pure magnesium using experimental and numerical methods. The finite element method with different ductile fracture models was employed to simulate plastic deformation and fracture behavior of the workpiece.

• Advances in concrete construction
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• 제3권4호
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• pp.253-268
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• 2015

This paper investigates the influence of various mix design parameters on the characteristics of concrete containing recycled coarse aggregates and Nano-Silica using Taguchi method. The present study adopts Water-cement ratio, Recycled Coarse Aggregate (%), Maximum cement content and Nano-Silica (%) as factors with each one having three different levels. Using the above mentioned control parameters with levels an Orthogonal Array (OA) matrix experiments of L9 (34) has selected and nine number of concrete mixes has been prepared. Compressive Strength, Split Tensile Strength, Flexural Tensile Strength, Modulus of Elasticity and Non-Destructive parameters are selected as responses. Experimental results are analyzed and the optimum level for each response is predicted. Analysis of 28 days CS depicts that NS (%) is the most significant factor among all factors. Analysis of the tensile strength results indicates that the effect of control factor W/C ratio is ranked one and then NS (%) is ranked two which suggests that W/C ratio and NS (%) have more influence as compared to other two factors. However, the factor that affects the modulus of elasticity most is found to be RCA (%). Finally, validation experiments have been carried out with the optimal mixture of concrete with Nano-Silica for the desired engineering properties of recycled aggregate concrete. Moreover, the comparative study of the predicted and experimental results concludes that errors between both experimental and predicted values are within the permissible limits. This present study highlights the application of Taguchi method as an efficient tool in determining the effects of constituent materials in mix proportioning of concrete.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 춘계학술대회 논문집 디스플레이 광소자분야
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• pp.86-89
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• 2004

Organic thin film transistors (OTFTs) are fabricated on the plastic substrate through 4-level mask process without photolithographic patterning to yield the simple fabrication process. And we herewith report for the effect of dielectric surface modification on the electrical characteristics of OTFTs. The KIST-JM-1 as an organic molecule for the surface modification is deposited onto the surface of zirconium oxide $(ZrO_2)$ gate dielectric layer. In this work, we have examined the dependence of electrical performance on the interface surface state of gate dielectric/pentacene, which may be modified by chemical properties in the gate dielectric surface.

• Transactions on Electrical and Electronic Materials
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• 제15권2호
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• pp.91-95
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• 2014

This paper presents the structure and process technology of simple and low-cost wafer-level packaging (WLP) for thin film radio frequency (RF) devices. Low-cost practical micromachining processes were proposed as an alternative to high-cost processes, such as silicon deep reactive ion etching (DRIE) or electro-plating, in order to reduce the fabrication cost. Gold (Au)/Tin (Sn) alloy was utilized as the solder material for bonding and hermetic sealing. The small size fabricated WLP of $1.04{\times}1.04{\times}0.4mm^3$ had an average shear strength of 10.425 $kg/mm^2$, and the leakage rate of all chips was lower than $1.2{\times}10^{-5}$ atm.cc/sec. These results met Military Standards 883F (MIL-STD-883F). As the newly proposed WLP structure is simple, and its process technology is inexpensive, the fabricated WLP is a good candidate for thin film type RF devices.

• Advances in nano research
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• 제5권1호
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• pp.27-34
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• 2017

One of the methods of removing cyanide from wastewater is surface adsorption. We simulated the removal of cyanide from a synthetic wastewater in the presence of Titanium dioxide nano-particles absorbent uses VISUAL MINTEQ 3.1 software. Our aim was to determine the factors affecting the adsorption of cyanide from synthetic wastewater applying simulation. Synthetic wastewater with a concentration of 100 mg/l of potassium cyanide was used for simulation. The amount of titanium dioxide was 1 g/l under the temperature of $25^{\circ}C$. The simulation was performed using an adsorption model of Freundlich and constant capacitance model. The results of simulation indicated that three factors including pH, nanoparticles of titanium dioxide and the primary concentration of cyanide affect the adsorption level of cyanide. The simulation and experimental results had a good agreement. Also by increasing the pH level of adsorption increases 11 units and then almost did not change. An increase in cyanide concentration, the adsorption level was decreased. In simulation process, rising the concentrations of titanium dioxide nanoparticles to 1 g/l, the rate of adsorption was increased and afterward no any change was observed. In all cases, the coefficient of determination between the experimental data and simulation data was above 0.9.

• 한국결정성장학회지
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• 제16권5호
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• pp.203-209
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• 2006

For $P_B=50,\;{\Delta}T=10K$, Ar=5, Pr=2.36, Le=0.015, Pe=1.26, Cv=1.11, the intensity of solutal convection (solutal Grashof number $Grs=3.44x10^4$) is greater than that of thermal convection (thermal Grashof number $Grt=1.81x10^3$) by one order of magnitude, which is based on the solutally buoyancy-driven convection due to the disparity in the molecular weights of the component A($Hg_2Cl_2$) and B(He). With increasing the partial pressure of component B from 10 up to 200 Torr, the rate is decreased exponentially. The convective transport decreases with lower g level and is changed to the diffusive mode at 0.1 $g_0$. In other words, for regions in which the g level is 0.1 $g_0$ or less, the diffusion-driven convection results in a parabolic velocity profile and a recirculating cell is not likely to occur. Therefore a gravitational acceleration level of less than 0.1 $g_0$ can be adequate to ensure purely diffusive transport.

• 한국진공학회지
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• 제17권1호
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• pp.40-45
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• 2008

유리기판 위에 약 500 nm 의 두께로 성장된 ZnO층의 구조적, 광학적, 전기적 성질에 미치는 갈륨도핑의 영향에 대하여 연구 하였다. 다결정 ZnO 와 GZO 층은 상온에서 radio frequency magnetron sputtering 법을 사용하여 성장되었다. 투과전자현미경 (TEM)과 x-ray 회절분석 (XRD)에 의하면, 갈륨이 도핑된 ZnO 박막의 결정성은 ZnO에 비하여 향상되었고 (002)방향을 따라 우선성장 되었음이 발견되었다. GZO 박막의 투과도는 가시광 영역에서 ZnO 박막에 비해 약 10% 정도 향상된 것으로 나타났다. PL 분석에 따르면, NBE emission 세기와 DL emission 세기의 비는 GZO 와 ZnO의 경우 각각 2.65:1 과 1.27:1로 나타났다. GZO와 ZnO의 비저항은 각각 1.27과 1.61 $\Omega{\cdot}cm$로서 GZO의 전기전도도가 높았다. GZO 와 ZnO의 캐리어농도는 각각 $10^{18}$ and $10^{20}cm^2$/Vs으로 측정되었다. 본 실험결과 따르면, Ga 도핑으로 인해 ZnO 박막의 전기적, 광학적, 구조적 특성이 향상되었음을 알 수 있었다.

• 식물병연구
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• 제25권4호
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• pp.179-187
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• 2019

이 연구는 플라즈마 기술 (radio frequency-thermal plasma system과 direct current sputtering system)을 이용하여 제작된 나노 금속복합체를 이용하여 박과 작물(수박, 호박, 박)의 종자에서 분리한 미생물의 항균 활성 효과를 검정하기 위하여 실험을 진행하였다. 8종의 나노 금속복합체와 4가지의 담체를 이용하여 5종의 곰팡이와 10종의 세균을 대상으로 기내 실험을 수행하였다. 그 결과, 곰팡이를 대상으로 한 항균실험에서 나노 금속복합체 Brass/CaCO₃의 경우 1,000 ppm 농도에서 5종의 곰팡이에 대하여 100%의 항균효과를 나타내었다. 세균을 대상으로 한 항균실험의 경우 나노 금속복합체 Brass/CaCO₃(1,000 ppm)은 Weissella sp., Rhodotorula mucilaginosa, Burkholderia sp. 그리고 Enterococcus sp. 4가지 세균을 100% 억제하는 것으로 확인되었다. 나노 금속복합체 G-Ni은 Rhizopus stolonifer에 대하여 100% 항균효과를 나타냈으며, 4가지 곰팡이에 대해서는 52.94-71.76% 정도의 항균효과를 나타내었다. 하지만 나노 금속복합체 G-Ni은 10종의 세균에 대해서는 효과가 없는 것으로 나타났다. 요약하면, 8가지 나노 금속복합체와 4가지 담체 중에서 Brass/CaCO₃가 5종의 곰팡이와 4종의 세균 대하여 항균효과가 있었으며, G-Ni는 5종의 곰팡이에 대해서 52.94-100% 효과를 보였으나 세균에 대해서는 항균효과가 없는 것으로 확인되었다.