• Journal of the Korean Geotechnical Society
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• v.28 no.11
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• pp.41-52
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• 2012

Suction drain method can directly apply vacuum pressure to the soft ground through vertical drains so it can make hardening zones around them. These hardening zones make steeply lower the discharge efficiency of the pore water with decreasing permeability. This paper considered a stepped vacuum pressure to minimize a hardening zone which is one of the important parameters that can decrease discharge efficiency. A series of laboratory tests were conducted in order to examine the effect of the hardening zones and to evaluate their effects to the ground improvements with varying durations which applied stepped vacuum pressures(-20kPa, -40kPa, -60kPa and -80kPa) with Busan marine clay. According to strength(CPT), water content test and theoretical investigation indicate a size of the hardening zone within 7cm and the decreasing ratio of permeability about 2.0~4.0. Also, the total settlements are larger for the stepped vacuum pressure than the instant vacuum loading. The application time with vacuum pressure is determined considering the geotechnical properties of the interested clays. Results of numerical analysis show that consolidation behavior is appropriate to measurement for considering hardening zones.

• Polymer(Korea)
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• v.30 no.2
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• pp.112-117
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• 2006

To improve the type error of osmotic tablet which is one of the drug delivery system, osmotic granule could be manufactured by fluidized bed coating. It has drug layer containing different amount of osmogant and is coated with membrane including different types of binder. We confirmed that the morphology of osmotic granule was different at each coating step. The more mont of osmotic agent, the faster drug release was observed due to increasing the driving force for drug release from osmotic granule. And drug release from osmotic granule coated with membrane using different types of binder was differed by solubility of binders to water. The formation of pore in membrane was confirmed by SEM and DSC Membrane using water soluble binder released more amount of drug. From these results, we assured that difference of osmotic pressure between the inside and the outside of granule and porosity of membrane have an effect on drug release from osmotic granule.

• Journal of the Korean Society for Railway
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• v.16 no.6
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• pp.473-481
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• 2013

The purpose of this research is to evaluate the improvements in the strength and injection range of loose ground after injecting $CaCO_3$(created by microorganism reaction). For this purpose, three cases of single-layer (Sand, SP, SW) specimens were made in a 150mm D ${\times}$ 200mm H space and two cases of multi-layer specimens (SW/SP, SP/SW) were made in a 150mm D ${\times}$ 300mm H space. The specimens were made with a relative density of 30% of soft ground and an injection was given over a time of one day. The uniaxial compression strength was measured with a cone penetrometer and the injection range was observed by checking the bulb formation around the injection nozzle. Also, the compositions of the specimens were assessed through XRD analyses. Based on the test results, a compressive strength of 500kPa and 15cm thick cementation were noted due to the cementation of the soil. This implies that there are significant effects of the pore condition and size on bio-grouting technology.

• Clean Technology
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• v.26 no.2
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• pp.131-136
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• 2020

Biomass bamboo charcoal is utilized as anode for lithium-ion battery in an effort to find an alternative to conventional resources such as cokes and petroleum pitches. The amorphous phase of the bamboo charcoal is partially converted to graphite through a low temperature graphitization process with iron oxide nanoparticle catalyst impregnated into the bamboo charcoal. An optimum catalysis amount for the graphitization is determined based on the characterization results of TEM, Raman spectroscopy, and XRD. It is found that the graphitization occurs surrounding the surface of the catalysis, and large pores are formed after the removal of the catalysis. The formation of the large pores increases the pore volume and, as a result, reduces the surface area of the graphitized bamboo charcoal. The partial graphitization of the pristine bamboo charcoal improves the discharge capacity and coulombic efficiency compared to the pristine counterpart. However, the discharge capacity of the graphitized charcoal at elevated current density is decreased due to the reduced surface area. These results indicate that the size of the catalysis formed in in-situ graphitization is a critical parameter to determine the battery performance and thus should be tuned as small as one of the pristine charcoal to retain the surface area and eventually improve the discharge capacity at high current density.

• Membrane Journal
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• v.8 no.3
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• pp.157-169
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• 1998

The effects of solvents (DMAc, NMP, 1,4-dioxane) and nonsolvents ($H_2O$, Methanol, n-hexane) on the morphology of 6FDA-p-TeMPD polyimide membrane, prepared by the wet phase inversion method, were studied. In the polymer/solvent/nonsolvent ternary system, the binodal curve, the coagulation value and the relative light transmission were measured, and the solubility parameter difference was calculated. The onset state and rate of liquid-liquid alemixing were predicted and the morphology of membrane was analyzed. It is found that the finger-like pores are formed within discontinuous polymer nodules when the binoclal curve is close to the polymer-solvent (P-S) axis, the coagulation value is small, the reduction of light transmission is easy to occur and the order of solubility parameter difference ($\Delta \delta_{i-j}$) is $\Delta \delta_{S-NS} > \Delta \delta_{P-NS} > \Delta \delta_{P-S}$. The dense skin with small nodules and the sponge type sublayer with macrovoid are formed in the case that the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is long and the order of $\Delta \delta_{i-j}$ is $\Delta \delta_{P-NS} >(\Delta \delta_{S-NS} < > \Delta \delta_{P-S})$. The thick layer of fine nodule coagulation and loosely grown sublayer of nodules appear when the binodal curve is distant from the P-S axis, the onset time of liquid-liquid demixing is very long and the order of $\Delta \delta_{i-j}$가 $\Delta \delta_{S-NS} > (\Delta \delta_{P-NS}$\lessgtr$ > (\Delta \delta_{P-NS} < >)\Delta \delta_{P-S}$ ).

• Journal of the Korea Organic Resources Recycling Association
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• v.10 no.2
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• pp.100-116
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• 2002

There are several purpose to introduce microorganism into the Soil. The major purpose is to promote plant growth and inhibit plant pathogens. The model example is to put in nitrogen fixing symbiotic bacteria, Pythium and Rhizobium. In order to achieve the intended goal, the introduced microorganism should survive and colonize with sufficient density. The survival of introduced microorganism depend upon biotic and abiotic factors. Predation and competition are important among biotic factor. Water tension, organic carbon, inorganic nutrients(N, P), pH are important factor among abiootic factor. Soil texture and distribution of soil pore are also important in the survival and colonization of introduced microorganism. Selection by soil ecosystem for inoculant is a crucial factor for colonization. Good example are control of autochtonous microorganism and the introduction of surfactant biodegrading Pseudomonas. Sometimes, carriers such as peat and montmorillonite can be added to help colonization. Carriers can protect introduced microorganism by supplying protective microhabitat. Organic polymer is also used as a carrier to immobilize bacteria or industrial enzymes. Examples of these carrier are calcium alginate, agarose and k-carrageenan. The function of these carrier is to provide microhabitat and help colonization for introduced microorganism.

• Korean Journal of Plant Taxonomy
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• v.42 no.2
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• pp.141-149
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• 2012

To clarify some ambiguous diagnostic characters of Callicarpa japonica Thunb. and Callicarpa dichotoma (Lour.) K. Koch in Korea (Verbenaceae), the external morphology and micromorphology (leaf, anther, pollen, fruit, in particular endocarp surface and structure) of two taxa are studied and described in detail. It is confirmed that the following characteristics (e.g., the stem outline in a cross-section, the bud shape and length, the corolla tube length and the lobe length, the pattern of the anther dehiscence and length, and the endocarp morphology) are useful for distinguishing these two taxa. In particular, following three characteristics are most useful for an identification: (1) the corolla tube length of C. japonica (2.5-4.6 mm) is longer than that of C. dichotoma (0.7-1.0 mm); (2) the anther is dehiscing by an apical pore at the anthesis of C. japonica, while it is opening by a long fissure from the apex to the base in C. dichotoma; and (3) the edge of the endocarp (lateral view) in C. japonica is concave, while in C. dichotoma it is shown to be flat. On the other hand, the teeth state on the leaf margin and the position of inflorescence are not good diagnostic characteristics for identification. Additionally, the keys for all known Callicarpa taxa in Korea are provided.

• Journal of the Korean Electrochemical Society
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• v.7 no.4
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• pp.183-188
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• 2004

In order to develop polymer electrolyte for lithium/sulfur batteries, highly microporous P(VdF-HFP) membranes were prepared by phase inversion method. Porous structure was controlled by extracting NMP with mixture of deionized water and methanol. Porous structure of the membranes was observed with SEM. Polymer electrolytes were prepared by soaking the porous membranes in 1M $LiCF_3SO_3-TEGDME/EC$. The ionic conductivity of polymer electrolyte was found to be at high as $2\times10^{-3}S/cm$ when the polymer membrane extracted by $80\%$ methanol was used. The microporous polymer electrolyte optimized in this work displayed high ionic conductivity, uniform pore size, low interfacial resistance and stable ionic conductivity with storage time. The ionic conductivity of polymer electrolytes was measured with various lithium salts, and the conductivity showed $3.3\times10^{-3}S/cm$ at room temperature when $LiPF_6$ was used as a lithium salt.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.241-241
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• 2008

Macrofore formation in silicon and other semiconductors using electrochemical etching processes has been, in the last years, a subject of great attention of both theory and practice. Its first reason of concern is new areas of macropore silicone applications arising from microelectromechanical systems processing (MEMS), membrane techniques, solar cells, sensors, photonic crystals, and new technologies like a silicon-on-nothing (SON) technology. Its formation mechanism with a rich variety of controllable microstructures and their many potential applications have been studied extensively recently. Porous silicon is formed by anodic etching of crystalline silicon in hydrofluoric acid. During the etching process holes are required to enable the dissolution of the silicon anode. For p-type silicon, holes are the majority charge carriers, therefore porous silicon can be formed under the action of a positive bias on the silicon anode. For n-type silicon, holes to dissolve silicon is supplied by illuminating n-type silicon with above-band-gap light which allows sufficient generation of holes. To make a desired three-dimensional nano- or micro-structures, pre-structuring the masked surface in KOH solution to form a periodic array of etch pits before electrochemical etching. Due to enhanced electric field, the holes are efficiently collected at the pore tips for etching. The depletion of holes in the space charge region prevents silicon dissolution at the sidewalls, enabling anisotropic etching for the trenches. This is correct theoretical explanation for n-type Si etching. However, there are a few experimental repors in p-type silicon, while a number of theoretical models have been worked out to explain experimental dependence observed. To perform ordered macrofore formaion for p-type silicon, various kinds of mask patterns to make initial KOH etch pits were used. In order to understand the roles played by the kinds of etching solution in the formation of pillar arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, N-dimethylformamide (DMF), iso-propanol, and mixtures of HF with water on the macrofore structure formation on monocrystalline p-type silicon with a resistivity varying between 10 ~ 0.01 $\Omega$ cm. The etching solution including the iso-propanol produced a best three dimensional pillar structures. The experimental results are discussed on the base of Lehmann's comprehensive model based on SCR width.

• Journal of Periodontal and Implant Science
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• v.35 no.3
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• pp.525-536
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• 2005

여러 연구들을 통해 많은 학자들이 임프란트 안정성(stability)은 표면의 특징에 달려있다고 생각하게 되었다. 표면의 구조, 에너지, 산화물(oxide) 두께와 표면성상(topography)등 임프란트의 표면의 특징은 임프란트와 골조직의 반응에서 중요한 역할을 하는 것이 알려짐에 따라 티타뮨 임프란트의 표면의 처리 방법에 큰 관심을 가지게 되었다. 그 중에서 티타늄 임프란트 표면의 산화피막화(anodization)가 한 방법으로 대두되었다. 이 방법은 전기화학적 방식으로 임프란트 표면에 거칠고(rough)두꺼우며(thick), 기공(pore)을 가지는 산화물 막을 형성하는 것으로 산화물의 두께는 coronal 부분(l-2 ${\mu}m$)으로부터 apical부분(7-10 ${\mu}m$)까지 증가하게 된다. 산화피막의 표면에는 다양한 크기의 수많은 기공이 주로 1-2 ${\mu}m$ 두께로 임프란트의 apical 부분에서 존재하며, 임프란트 표면의 거칠기는 conical 위부분에서 apical 부분까지 계속 증가한다(평균 Ra value=1.2 ${\mu}m$). 또 다른 표면 처리 방법으로는 blasting 후에 etching을 한 SLA 표면이 있다. 이 연구의 목적은 일반적으로 많이 이용되고 있는 anodized 표면과 SLA 표면의 조직학적 반응을 비교 분석하는 것이다. 24개 임프란트를(anodized surfaced implant-12개 , SLA-12개, 8mm ${\times}\;{\Phi}$ 4.3) 6마리 토끼의 오른쪽과 왼쪽 femur에 식립하였다. 12주후에 동물들을 희생하여 EXACT cutting-grinding system을 이용하여 샘플을 절단하고 800, 1200 및 4000 번 연마제(abrasive) paper로 20-50 ${\mu}m$ 까지 grinding하였다. 샘플은 Multiple staining 용액으로 염색하여 SLA 임프란트 군과 비교하였다. 골과 임프란트 사이에 연결을 TDI 프로그램을 이용하여 %로 측정하였다. SLA 임프란트 군 경우에는 골과 임프란트 사이의 연결이 $74{\pm}19%$ 이고, 양극 산화한 임프란트 군 경우에는 $77{\pm}9%$이었다. 양극 산화한 티타늄 임프란트의 골 접촉률이 SLA 표면 임프란트 경우과 통계학적으로 유의한 차이는 보이지 않았다.