109,854 research outputs found
Construction heuristics for two-dimensional irregular shape bin packing with guillotine constraints
No full textThe paper examines a new problem in the irregular packingliterature that has existed in industry for decades;two-dimensional irregular (convex) bin packing with guillotineconstraints. Due to the cutting process of certain materials, cutsare restricted to extend from one edge of the stock-sheet toanother, called guillotine cutting. This constraint is commonplace in glass cutting and is an important constraints intwo-dimensional cutting and packing problems. In the literature,various exact and approximate algorithms exist for finding the twodimensional cutting patterns that satisfy the guillotine cuttingconstraint. However, to the best of our knowledge, all of thealgorithms are designed for solving rectangular cutting where cutsare orthogonal with the edges of the stock-sheet. In order tosatisfy the guillotine cutting constraint using these approaches,when the pieces are non-rectangular, practitioners implement a twostage approach. First, pieces are enclosed within rectangle shapesand then the rectangles are packed. Clearly, imposing this condition is likely to lead to additional waste. Thispaper aims to generate guillotine-cutting layouts of irregularshapes using a number of strategies. The investigation comparestwo two-stage approaches; one approximates pieces by rectangles,the other approximates pairs of pieces by rectangles usingphi-functions for optimal clustering. Both these approaches usestate of the art rectangle bin packing with guillotineconstraints. Further, we design and implement a one-stage approachusing a self-adapted forest search algorithm. Experimental resultsshow the one-stage strategy to produce good solutions in less timeover the two-stage approach
탄소나노튜브를 이용한 field emitters의 제조공정 및 전계방출특성 연구
No full text학위논문(박사) - 한국과학기술원 : 신소재공학과, 2009.2, [ xii, 178 p. ]Carbon nanotubes (CNTs) have excellent field emission properties but there are critical problems to be solved in order to use CNTs as high performance field emitters in various application areas. Application of CNT field emitters can be categorized into two areas. One category is planar applications which use array type CNT field emitters such as FED and BLU. The other category is point electron source applications which use tip type CNT field Emitters such as X-ray tube and electron microscopy.
Thus, CNT field emitters should be designed carefully according to the specific applications. In case of array type CNT field emitters for FED and BLU, the critical issues are stability and uniformity at large area. On the other hand, in case of tip type CNT field emitters for X-ray tube, the critical issues are high resolution and stability. Based on these requirements, different research strategies were suggested and different types of materials were fabricated and characterized. For the array type CNT field emitters, CNT nanocomposite powders were fabricated by molecular level mixing process and in-situ spray coating process was developed. For the tip type CNT field emitters, CNT yarn was fabricated and its properties were investigated.
For the array type CNT field emitters, CNT/Co nanocomposite powders were successfully fabricated by polyol process and in-situ spray coating process. CNT/Co nanocomposite powders showed necklace type structure with small size distribution. CNT/Co nanocomposite field emitters by in-situ spray coating process showed better field emission properties in terms of turn-on field and stability compared to the screen printed one. The enhanced field emission properties were attributed to the self-activation of CNTs and minimized destruction of CNTs. Thus, the in-situ spray coating process is quite promising for fabrication of high performance field emitter based on CNT/Metal nanocomposites.
In order to solve problems of CNT/Co nanocompos...한국과학기술원 : 신소재공학과
Development and application of micro transfer stamping technique
No full text本論文以開發微轉印技術為主軸，研究快速簡單的製程技術製作微結構。此製程主要特色有五：1.製程單純；2.所製作的微結構無殘留層，不須額外去除殘留層步驟，有效降低製程複雜性，並提高可應用材料之多樣性；3.可製作多層微結構；4.製程相容性高，只要是可溶液製程(solution-processable)之材料皆可進行轉印；5.無須額外化學方法即可進行轉印。論文主要研究內容包括：金屬黃光顯影蝕刻製程之開發、ITO薄膜蝕刻製程之開發、PDMS模具於轉印製程之應力分析與模擬、單層與雙層微轉印製程之開發以及微轉印製程之應用等部分。「金屬黃光顯影蝕刻製程開發方面」，本研究藉著氯化鐵蝕刻液對銅與不鏽鋼進行蝕刻，並建立製程參數。在「ITO薄膜蝕刻」之研究方面，研究結果顯示四個製程因子會對ITO蝕刻結果產生很大的影響，並提出搭配適當的光阻塗佈厚度與曝後烤，可以有效降低ITO薄膜蝕刻後尺寸改變的問題。在「PDMS模具轉印之應力分析」部分，模擬結果顯示垂直方向壓力會致使PDMS模具微結構間間隙產生垂直方向的位移，可能導致轉印殘留層的產生。模擬結果更提出藉著改變PDMS模具厚度可以有效降低間隙垂直位移量，防止殘留層產生。在「單層與雙層轉印製程之開發」方面，本論文證實藉著溫度與壓力適當的調配，光阻墨水可完整轉印至壓克力基材上，且無殘留層產生。搭配自製的對位系統，更可以轉印出雙層微結構，包含堆疊的圓點結構與交錯的光柵結構。同時也對濕式、乾式轉印進行製程探討，以增加製程適用之範圍。在「微轉印製程之應用」方面，本研究驗證轉印製程可直接轉印光阻於銅片上，做為蝕刻擋罩，而不需經過黃光微影製程。另外本研究也轉印參雜過的導電高分子材料，以印證使用轉印技術具有製作有機薄膜電晶體(field-effect transistor, TFT)的能力。The thesis develops a micro transfer stamping technique to fabricate microstructures. There are five advantages of the micro transfer stamping technique： 1. This is a simple process; 2. There is no residual layer, therefore no additional process is needed to remove the residual layer; 3. The process can fabricate muti-layer structure; 4. The process is theoretically suitable for all solution-processable materials; 5. No additional chemical process is needed in the process.here are five research topics in the thesis, includes development of lithography and etching process for metal materials, development of ITO etching process, stress and strain simulation of PDMS mold in the transfer stamping process, development of single-/ muti- layer transfer stamping process and application of the micro transfer stamping process.n the “development of lithography and etching process for metal materials” section, FeCl3 is used to etch metals including cooper and stainless steel, and the suitable process parameters are identified. In the “development of ITO etching process” section, optimization of four process factors of the ITO etching quality is carried out. In the section, we propose that with proper PR coating thickness and post expose baking time, the desired dimensions of ITO pattern can be reached. In the “stress and strain simulation of PDMS mold in the transfer stamping process” section, the simulation results show that the “gap” between microstructures of PDMS mold sags as the applied pressure is high enough or the gap length is large. A large sagging distance would lead to residual layer appearance in the transfer stamping process. It is found that increasing PDMS mold thickness can prevent residual layer forming. In the “development of single/ multi-layer transfer stamping process” section, the micro transfer stamping technique can effectively transfer the patterns of the mold onto substrate. With proper pressure and temperature, the PR “ink” can successfully be transferred on the PMMA substrate with no residual layer. The section also proves that the micro transfer stamping technique can transfer dual-layer patterns, including spot stacks and woven patterns. In the “application of the micro transfer stamping process” section, we show the application of micro transfer stamping technique. The single-layer transferred PR patterns can replace lithography process, to be directly used as the etching mask in the metal-etching process. We also prove that the micro-transfer stamping can transfer various materials, including doped conductive polymer, PEDOT:PSS and silver paste. This implies that the process has the potential to fabricate muti-layer organic field effect transistor (TFT).致謝 I文摘要 II文摘要 III目錄 VIII目錄 IX一章 導論 1.1 多層結構製作技術介紹 1.2應用塑膠高分子材料轉印技術優勢 2.3 有機薄膜電晶體元件 3.4研究動機與研究架構 3.5論文架構 4二章 文獻回顧 9.1 結構轉印技術 9.2浮雕轉印技術 10.3 多層結構元件轉印技術 10.4有機薄膜電晶體元件介紹 12.4.1 薄膜電晶體之作用原理 12.4.2 有機半導體材料 14.5 有機薄膜電晶體(OTFT)製程相關文獻 15.6 文獻總體回顧與研究創新 17三章 實驗流程與初步製程探討 30.1 實驗流程與方法 30.2光微影與蝕刻法製程介紹 31.2.1 試片前處理工作 31.2.2 光微影製程與蝕刻製程 31.2.3 本研究運用之光阻 33.3微影與蝕刻製程測試結果討論 34.3.1 微影製程 34.3.2 顯影結果與討論 35.3.3蝕刻製程 35.3.4蝕刻結果與討論 35.4 PDMS軟式模具之備製 37.4.1 PDMS材料介紹 37.4.2 PDMS模具翻印 37.5 ITO蝕刻製程開發 38.5.1 ITO薄膜介紹 38.5.2 ITO薄膜蝕刻製程 38.5.3 ITO薄膜蝕刻結果與討論 39.5.4 ITO薄膜蝕刻總結 41四章 軟式模具轉印之模擬與分析 56.1 PDMS模具轉印時變形狀態分析 56.1.1 圓柱結構變形狀況分析 56.1.2 光柵結構變形狀況分析 57.2 有限元素法簡介 57.2.1有限元素法 58.2.2有限元素分析求解軟體ABAQUS 58.2.3模擬之單位系統 59.3初步模型與模擬參數之建立 59.3.1 PDMS軟模與PMMA基材2D模型建立 59.3.2接觸條件之設定 60.3.3邊界條件設定 60.3.4元素選擇 61.3.5網格製作 61.3.6 Nlgeom設定 61.4初步模擬結果與討論 62.5模擬結果對照轉印參數分析與討論 62.5.1 模具厚度差異與gap寬度差異分析 63.5.2 施加壓力差異分析 64.5.3 2D模擬總結 64五章 轉印製程與多層轉印製程之開發研究 74.1 轉印製程介紹 74.2 轉印製程設計與開發 74.2.1 轉印製程實驗之材料 74.2.2 加壓方法介紹 75.2.3 轉印機制與表面間黏著力 75.2.4 表面能控制—轉印溫度 76.2.5 表面能控制—轉印墨水材料 77.3 單層圖型轉印製程與結果 77.3.1 轉印結構與模具 77.3.2 初步轉印製程與步驟 78.3.3 濕式轉印製程初步轉印結果 78.4 濕式轉印製程探討 79.4.1 濕式轉印製程轉印溫度探討 79.4.2 轉印壓力探討 80.4.3轉印MT-UV 6002光阻 80.4.4 塗佈時間探討 81.5 乾式單層轉印結果與討論 82.5.1 製程與模具 82.5.2 轉印結果與初步探討 82.5.3轉印壓力與轉印溫度對乾式轉印結果之影響 82.5.4 轉印均勻度之提升 83.6 多層轉印製程開發 83.6.1 對位機制 84.6.2 交錯式光柵圖案轉印結果與探討 84.6.3 堆疊圓點圖案轉印結果與探討 84.6.4 PMMA基材受熱與壓力下陷量探討 85.7 轉印銀膠墨水與導電高分子墨水 85.7.1 轉印墨水表面能觀察 85.7.2 旋塗墨水方式調整 86.7.3 PEDOT:PSS導電高分子轉印製程與結果 87.7.4 導電銀膠轉印製程與結果 87.8 轉印製程之另一應用 - 銅蝕刻擋罩 88.9 轉印製程總結 88六章 開發轉印製程製作薄膜電晶體 110.1 簡介 110.1.1 半導體層材料—P3HT 110.1.2 源極/汲極導電材料—銀膠與PEDOT:PSS 111.1.3 介電層—PMMA與PVP 111.1.4 閘極與基材 112.2TFT各層製程探討 112.2.1 光罩設計與模具製作 112.2.2閘極製作 112.2.3 介電層製作 113.2.4 使用濕式轉印法製作汲極/源極 114.2.5 使用乾式轉印法製作P3HT半導體(主動)層 116.3 O-TFT製作總結 117七章 結論與未來展望 125.1 結論 125.2 原始貢獻 127.3 未來研究方向與展望 128考文獻 130錄A 作者簡歷 135錄B 著作 13
화학공정법을 이용한 콜로이달 금속 나노입자의 합성 및 특성 평가
No full text학위논문(석사) - 한국과학기술원 : 신소재공학과, 2004.8, [ ix, 69 p. ]Colloidal metallic nanoparticles have unique optical, electrical, magnetic and thermal properties and many applications such as biosensors, high-density recording medias, magnetic fluids, drug deliveries and gene therapies. The physical and chemical properties of colloidal nanoparticles are dependent not only on the materials system but also on their size and shape. Therefore, monodispersed nanoparticles with controlled shape are required for many applications of colloidal nanoparticles.
In order to fabricate monodispersed metallic nanoparticles, several chemical processes were proposed during the last decade. Among them, polyol process has been employed for the synthesis of colloidal metallic and bimetallic nanoparticles. In the polyol process, the polyol (two or more ) acts as reducing agent, solvent and stabilizer, simultaneously. Recently, the polyol process has been modified for the synthesis of noble metal seeds or nuclei prior to the coating of another metallic material that does not nucleate homogeneously. However, the polyol process is a relatively slow reaction process compared to the thermal decomposition process. It, usually, takes several hours for nucleation and growth of nanoparticles without any additives. Although it is not beneficial to use the polyol process for synthesis of the monodispersed nanoparticles, it provides many opportunities to change and control the particle size and shape during the process. So far, only the ethylene glycol and PVP (polyvinylpirrolidone) have been used for the typical polyol process and there have been few attempts to modify it.
In this study, the polyol process was modified, i.e., the octylether, which is long chain polyol (1,2-hexadecanediol), and long alkyl chain surfactants were used as solvent, reducing agent and stabilizer, respectively. By using the modified polyol process, the relationship between process parameters and size and shape of colloidal metallic nanoparticles were investigated.
It wa...한국과학기술원 : 신소재공학과
500 expedicionariops europeos visitarán ruinas de Chan Chan. Trujillo da hoy la bienvenida a jóvenes turistas
No full text500 expedicionariops europeos visitarán ruinas de Chan Chan. Trujillo da hoy la bienvenida a jóvenes turistas. Documento que forma parte de la colección documental "Recortes periodísticos del Instituto Nacional de Cultura [LIB-130101-IIG-IIG-000-15-07-1995]Dicha información no refleja necesariamente la posición institucional del Ministerio de Cultura
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