• Title/Summary/Keyword: Layer-by-Layer assembly

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Nondestructive testing for the evaluation of adhesive layer in rocket motor case assembly (연소관 조립체 접합계면의 평가를 위한 비파괴시험에 관한 연구)

  • 박준수;송성진;김영환;임수용;윤남균;조정표
    • Proceedings of the Korean Society of Propulsion Engineers Conference
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    • 2001.11a
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    • pp.90-93
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    • 2001
  • In the present work, ultrasonic testing method has been developed to evaluate adhesive layers in rocket motor case assembly for the reliability of the rocket. The main objective of the present work was to find debonding between steel and rubber layers. The relationship between adhesion ratio and reflected ultrasonic amplitude was calculated by considering reflection coefficient at the interface between steel and rubber layers. It was found that the higher amplitude of ultrasound is reflected for the debonding area, and shown good agreements with experimental results. The ultrasonic C-scan images offers good implements for the determination of debonding area. The nondestructive testing results were compared with the micrography of destruective testing. As results, ultrasonic testing could be utilized for the evaluation of adhesive layer in the rocket motor case assembly.

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Neural Network Model-based Algorithm for Identifying Job Status in Block Assembly Shop for Shipbuilding (신경망 모델 기반 조선소 조립공장 작업상태 판별 알고리즘)

  • Hong, Seung-Taek;Choi, Jin-Young;Park, Sang-Chul
    • IE interfaces
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    • v.24 no.3
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    • pp.267-273
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    • 2011
  • In the shipbuilding industry, since production processes are so complicated that the data collection for decision making cannot be fully automated, most of production planning and controls are based on the information provided only by field workers. Therefore, without sufficient information it is very difficult to manage the whole production process efficiently. Job status is one of the most important information used for evaluating the remaining processing time in production control, specifically, in block assembly shop. Currently, it is checked by a production manager manually and production planning is modified based on that information, which might cause a delay in production control, resulting in performance degradation. Motivated by these remarks, in this paper we propose an efficient algorithm for identifying job status in block assembly shop for shipbuilding. The algorithm is based on the multi-layer perceptron neural network model using two key factors for input parameters. We showed the superiority of the algorithm by using a numerical experiment, based on real data collected from block assembly shop.

Functional Layer-by-Layer Assembled Multilayers Based on Nucleophilic Substitution reaction

  • Jo, Jin-Han
    • Proceedings of the Materials Research Society of Korea Conference
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    • 2011.05a
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    • pp.9.2-9.2
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    • 2011
  • Ultrathin polyelectrolyte (PE) multilayer films prepared by the versatile layer-by layer (LbL) assembly method have been utilized for the preparation of light-emitting diodes, electrochromic, membrane, and drug delivery system, as well as for selective area patterning and particle surface modification because the various materials with specific properties can be inserted into the film with nano-level thickness irrespective of the size or the shape of substrate. Since the introduction of the LbL technique in 1991 by Decher and Hong, various hydrophilic materials can be inserted within LbL films through complementary interactions (i.e., electrostatic, hydrogen-bonding or covalent interaction). In this study, it is demonstrated that LbL SA multilayer films based on nucleophilic substitution reaction can allow the preparation of the highly efficient magnetic and/or optical films and nonvolatile memory devices.

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Electrochemical Property of Immobilized Spinach Ferredoxin on HOPG Electrode

  • Nam Yun-Suk;Kim, You-Sung;Shin, Woon-Sup;Lee, Won-Hong;Choi, Jeong-Woo
    • Journal of Microbiology and Biotechnology
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    • v.14 no.5
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    • pp.1043-1046
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    • 2004
  • The stability and electrochemical properties of a self-assembled layer of spinach ferredoxin on a quartz substrate and on a highly oriented pyrolytic graphite electrode were investigated. To fabricate the ferredoxin self-assembly layer, dimyristoylphosphatidylcholine was first deposited onto a substrate for ferredoxin immobilization. Surface analysis of the ferredoxin layer was carried out by atomic force microscopy to verify the ferredoxin immobilization. To verify ferredoxin immobilization on the lipid layer and to confirm the maintenance of redox activity, absorption spectrum measurement was carried out. Finally, cyclic-voltammetry measurements were performed on the ferredoxin layers and the redox potentials were obtained. The redox potential of immobilized ferredoxin had a formal potential value of -540 mV. It is suggested that the redox-potential measurement of self-assembled ferredoxin molecules could be used to construct a biosensor and biodevice.

Fabrication of an Alternating Multilayer Film of Poly(ethylene-alt-maleic anhydride) and Poly(4-vinyl pyridine) by Layer-by-Layer Self-Assembly Method (Layer-by-Layer 자기조립법에 의한 Poly(ethyiene-alt-maleic anhydride)i Poly(4-vinyl pyrtdine) 다층막 제조)

  • Lee Joon Youl;Hong Sook-Young
    • Polymer(Korea)
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    • v.29 no.4
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    • pp.392-398
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    • 2005
  • Self-assembled multilayer thin films of poly(ethylene-alt-maleic anhydride) (PEMAh) and poly(4-vinyl pyridine) (P4VP) were fabricated by layer-by-layer (LbL) sequential adsorption. Fourier transform infrared (FT-IR) spectroscopic analysis of the self-assembled PEMAh/P4VP multilayer films confirms that the driving forces for the multilayer buildup are the intermolecular hydrogen bonding and electrostatic interactions. The linear increase of absorption peak of P4VP at 256 nm with increasing number of PEMAh/P4VP bilayers indicates that the multilayer buildup is an uniform assembling process. We also investigate the effects of polyelectrolyte concenhation variation of the dipping solution and pH variation of the PEMAh solution on the multilayer film formation. Thickness. adsorbed polyelectrolyte mass and surface roughness of the multilayer films were measured by UV-visible spectroscopy, quartz crystal microbalance (QCM), and atomic force microscopy (AFM), respectively.

Design Factors of Membrane Electrode Assembly for Direct Methanol Fuel Cells. (직접 메탄올 연료전지용 막-전극 접합체의 설계 인자에 관한 연구)

  • Cho, Jae-Hyung;Hwang, Sang-Youp; Kim, Soo-Kil;Ahn, Dong-June;Lim, Tae-Hoon;Ha, Heung-Yong
    • Clean Technology
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    • v.13 no.4
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    • pp.293-299
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    • 2007
  • Direct coating of catalyst layer on the $Nafion^{(R)}$ membrane has been optimized in the process of fabrication of membrane electrode assembly (MEA) to enhance the performance of direct methanol fuel cell (DMFC). In this method, the contact resistance at the interface of the catalyst layer and the membrane was found to be low. The effect of catalyst loading, thickness of membrane and the gas diffusion layer (GDL) with or without the presence of micro-porous layer (MPL) on the performance of the MEA was also investigated. The MEA fabricated by the above-mentioned method exhibited a performance of $147\;mW/cm^2$ and $100\;mW/cm^2$ at $80^{\circ}C$ and $60^{\circ}C$, respectively, with the catalysts loading of $4\;mg/cm^2$.

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Humidity-Sensitive Properties of Self-Assembled Polyelectrolyte System

  • Lee Chil-Won;Kim Jong-Gyu;Gong Myoung-Seon
    • Macromolecular Research
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    • v.13 no.3
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    • pp.265-272
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    • 2005
  • Polyelectrolyte membranes for humidity-sensing were fabricated using a layer-by-layer adsorption process based on the spontaneous self-assembly of alternating layers of cationic and anionic polymers on a silanized ITO patterned glass substrate. The substrate is dipped successively into dilute solutions of a polyanion and a polycation. The homopolymers and copoymers of diallyldimethylammonium chloride (DDA), allylamine hydrochloride (AA), 2-[(methacryloyloxy)ethyl]trimethyl ammonium chloride (METAC) and vinylbenzyl tributyl phosphonium chloride(VTBPC) were used as the polycations. In this experiment, it was found that the resistance varied according to the chemical structure of the polycation. The resistance varied from $10^7$ to $10^5$ $\Omega$, as the humidity was increased from 60 (relative humidity) to $95\%$RH, which is the range of RH values required for a dew sensor operating at high humidity.

Highly Stable Photoluminescent and Magnetic Multilayers Using Nucleophilic Substitution Reaction in Organic Media

  • Jo, Jin-Han
    • Proceedings of the Korean Vacuum Society Conference
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    • 2010.08a
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    • pp.262-262
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    • 2010
  • We introduce a novel and efficient strategy for producing free-standing functional films via photo-crosslinking and electrostatic layer-by-layer (LbL) assembly, which can allow the buildup of hydrophilic multilayers onto hydrophobic surfaces. Hydrophobic multilayers were deposited on ionic substrates by a photo-crosslinking LbL process using photo-crosslinkable polymers. The photo-crosslinked surface was converted to an anionic surface by excess UV light irradiation. This treatment allowed also the stable adhesion between metal electrode or cationic polyelectrolyte and hydrophobic multilayers. After dissolving the ionic substrates in water, the formed free-standing films exhibited unique functionalities of inserted components within hydrophobic and/or hydrophilic multilayers.

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Deposition and Characterization of Antistiction Layer for Nanoimprint Lithography by VSAM (Vapor Self Assembly Monolayer) (기상 자기조립박막 법을 이용한 나노임프린트용 점착방지막 형성 및 특성평가)

  • Cha, Nam-Goo;Kim, Kyu-Chae;Park, Jin-Goo;Jung, Jun-Ho;Lee, Eung-Sug;Yoon, Neung-Goo
    • Korean Journal of Materials Research
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    • v.17 no.1
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    • pp.31-36
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    • 2007
  • Nanoimprint lithography (NIL) is a new lithographic method that offers a sub-10nm feature size, high throughput, and low cost. One of the most serious problems of NIL is the stiction between mold and resist. The antistiction layer coating is very effective to prevent this stiction and ensure the successful NIL results. In this paper, an antistiction layer was deposited by VSAM (vapor self assembly monolayer) method on silicon samples with FOTS (perfluoroctyltrichlorosilane) as a precursor for making an antistiction layer. A specially designed LPCVD (low pressure chemical vapor deposition) was used for this experiment. All experiments were achieved after removing the humidity. First, the evaporation test of FOTS was performed for checking the evaporation temperature at low pressure. FOTS was evaporated at 5 Tow and $110^{\circ}C$. In order to evaluate the temperature effect on antistiction layer, chamber temperature was changed from 50 to $170^{\circ}C$ with 0.1ml of FOTS for 1 minute. Good hydrophobicity of all samples was shown at about $110^{\circ}$ of contact angle and under $20^{\circ}$ of hysteresis. The surface energies of all samples calculated by Lewis acid/base theory was shown to be about 15mN/m. The deposited thicknesses of all samples measured by ellipsometry were almost 1nm that was similar value of the calculated molecular length. The surface roughness of all samples was not changed after deposition but the friction force showed relatively high values and deviations deposited at under $110^{\circ}$. Also the white circles were founded in LFM images under $110^{\circ}$. High friction forces were guessed based on this irregular deposition. The optimized VSAM process for FOTS was achieved at $170^{\circ}C$, 5 Torr for 1 hour. The hot embossing process with 4 inch Si mold was successfully achieved after VSAM deposition.

Preliminary Study on Properties of Layer-by-Layer Assembled GCC with Polyelectrolytes (고분자전해질의 LbL 흡착 처리에 의해 개질된 중질탄산칼슘의 특성 기초 연구)

  • Lee, Je-Gon;Ryu, Jae-Ho;Sim, Kyu-Jeong;Ahn, Jung-Eon;Lee, Hak-Lae;Youn, Hye-Jung
    • Journal of Korea Technical Association of The Pulp and Paper Industry
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    • v.43 no.3
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    • pp.35-42
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    • 2011
  • In this study, ground calcium carbonate (GCC) was modified by Layer-by-Layer (LbL) multilayering with polyelectrolytes. Cationic polyacrylamide (C-PAM) and poly sodium 4-styrene sulfonate (PSS) were used as cationic and anionic polyelectrolytes to modify GCC. The characteristics of the modified GCC were examined in terms of zeta potential and particle size with the addition level of polyelectrolyte and layer number. The GCC could form an assembly of cationic and anionic polyelectrolytes through consecutive adsorption process. The zeta potential of the modified GCC moved toward the cationicity and reached the plateau with the increase of the addition level of C-PAM. With layering of anionic PSS, the GCC had the negative charge. The particle size was dependent on the zeta potential. It was also observed by optical microscope. As the PSS was in the presence of the outermost layer, the GCC showed the better dispersability. It indicated that the surface charge and particle size can be controlled by adjusting the addition level of polyelectrolyte and the layer number.