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Formation Mechanism of Mg Thin Films of Nano Granular Structure Prepared by Thermo-electron Activated Ion Plating Method and Their Corrosion Resistance
Get PDFMagnesium is the lightest metal among all structural metals(35% lighter than aluminium) and has a good strength-to-weight ratio, vibration resistance and EMR shield, etc.. Moreover, it is plentiful element, consisting 2.7% of earths crust and 0.13% of major source in ocean. Accordingly, it forms the basis for commercial alloys that have found to be used in a wide variety of application such as automobile, aircraft components, note book computer case, cellular phone case etc..
However, magnesium has not been applied as much as aluminum because of its insufficient corrosion resistance in neutral and acid environment. Therefore, in general, magnesium is used for coating techniques by wet process such as chromate surface treatment, and anodizing etc.. But these coating techniques entail durable and environmental problems. Moreover, it raises recycling problems which are related to the mixing of impurities.
In general, light metals, particularly magnesium, are difficult to plate using conventional coating techniques such as chemical or electro-chemical processes. This is due to the presence of the easy formation of oxide layer. In order to limit oxidization during coating, vacuum deposition techniques can be used as an alternative to conventional techniques operating in wet or in air conditions. It is well known that coated films, particularly those deposited from plasma-assisted vacuum coating technique, are usually quite different from the respective bulk material as to their structures and properties. For this reason, the use of plasma-assisted techniques, e.g., physical vapor deposition such as ion-plating method, has spreaded into various types of industrial applications. However, few studies have been reported dealing with magnesium metal and using the new techniques.
In this work, magnesium thin films were prepared on magnesium alloy(AZ91D and AZ31) substrate by environmental friendly coating technique of thermo-electron activated ion-plating method. The influence of gas pressure and substrate bias voltages on the crystal orientation and morphology of the films was determined by using X-ray diffraction and field emission scanning electron microscopy(FE-SEM), respectively. And the effect of crystal orientation and morphology of the magnesium thin films on corrosion behavior was estimated by measuring electro-chemical anodic polarization curves in deaerated 3% NaCl solution. Besides, hardness of these films were measured by knoop micro-hardness tester.
From the experimental results, all the deposited magnesium films showed obviously good corrosion resistance to compare with 99.99% Mg-ingot for evaporation metal and AZ91D for substrate. And magnesium film of morphology changed from columnar to granular structure with an increase of gas pressure. And the diffraction peaks of magnesium film became less sharp and broadened with the increase of gas pressure. The morphology of the films depended not only on gas pressure but also on bias voltage, i.e., the effect of increasing bias voltage was similar to that of decreasing gas pressure. The influences of gas pressures and bias voltages can be explained by applying the effects of adsorption and occlusion and argon gas. Finally, it was shown that the properties of magnesium films can be improved greatly by controlling the crystal orientation and morphology with effective use of the plasma ion plating technique.목차
Abstract
제1장 서론 = 1
제2장 기본 이론 = 6
2.1 표면 = 6
2.1.1 금속의 표면 = 6
2.2 여러 가지 표면반응 = 10
2.2.1 분자의 흡착 = 10
2.2.2 산화와 환원 = 14
2.2.3 금속의 부식 = 21
2.3 여러 가지 표면개질 방법 = 30
2.3.1 플라즈마 = 30
2.3.2 플라즈마를 이용한 표면처리 = 35
2.4 박막 = 54
2.4.1 박막의 정의 = 54
2.4.2 박막의 특징 = 55
2.4.3 박막의 형성 = 56
제3장 실험방법 = 68
3.1 실험장치 = 68
3.2 시편준비 = 71
3.3 Mg 박막의 제작 = 72
3.4 Mg 박막의 특성 분석 및 평가 = 73
3.4.1 Mg 박막의 Morphology 관찰 = 73
3.4.2 Mg 박막의 결정구조 분석 = 75
3.4.3 Mg 박막의 내식 특성 평가 = 77
3.4.4 Mg 박막의 경도 특성평가 = 79
제4장 실험결과 및 고찰 = 80
4.1 Ar 가스압의 변화에 의해 제작한 Mg 박막의 Morphology 및 결정배향성 = 81
4.1.1 Mg 박막의 표면 및 단면의 Morphology 관찰 = 81
4.1.2 Mg 박막의 결정배향성 분석 = 90
4.1.3 Ar 가스의 흡착 및 흡장에 의한 Mg 박막의 형성관계 고찰 = 99
4.2 Mg 박막의 특성 평가 = 105
4.2.1 Mg 박막의 내식특성 = 105
4.2.2 Mg 박막의 경도특성 = 122
제5장 결론 = 125
참고문헌 = 12
A Study on Sceuring the Waterfront in Port Development of Korea
Get PDFThe major ports around the world are trying to build not only durable environmentally sound ports but also create a nice waterfront area which goes with the port. and we should not over look these world trends.
Thus, the aim of this study is to convert modern cognition and this study began on the faith that the systematic development of waterfront space can act on a continuous energy of port competition.
Chapter 1 is an explanation of the purpose of the study, Chapter 2 is an explanation of the terms that were used in the study.
In chapter 3, we study about the examples of foreign development waterfront, In the case of the U. S. and Europe was focused on they redevelopment of ports and in the case of Japan, we focused on the insurance of the waterfront that goes with the port institution during this development process between the new-port and the new-city.
In our country, we can compare both cases.
The necessity of both new developments and redevelopments is appears right now and will continue to appear in the future.
In chapter 4, we will discuss the present conditions of ports, for example the port development policy of Korea and the presence of waterfront space, in regard to the ports as well as study for the waterfront plans in Korea.
In Korea all kind, of development and investment planners in ports is taken by the central government.
In Korea, the actual results for waterfront area assistance is quite low but because of the ports function and redevelopment plans, the demands for waterfront area inside of port will increase.
And in chapter 4, there is a waterfront area plan that regarded to new port development and an old port redevelopment.
Korea has a plan to develop a waterfront area by investing one trillion two hundred eighty two billion won in all the main ports till 2020.
In chapter 4 we study about the desirable direction of port waterfront development and the necessity for this development.
Finally, in chapter 5, is a conclusion to this study.
In the case of Korea, redevelopment of and new development to port are happening to the came time. And the management of the ports can be converted from government control to the PA (Port Authority).
So, the participation of citizen will be more magnified.
In all of these plans, the nations of waterfront should not be excluded.
We have to follow the previous success of other developed countries and develop a waterfront that is good for our environment, and for this, special effort and studies are required.목차
제1장 서론 = 9
제2장 항만친수공간의 개념적 고찰 = 11
제1절 항만의 정의와 기능 = 11
1. 항만의 정의 = 11
2. 항만의 요건 및 기능 = 12
제2절 워터프런트(Waterfront)의 정의 및 유형 = 15
1. 워터프런트의 정의 및 범위 = 15
2. 워터프런트의 기능 및 유형 = 19
3. 워터프런트의 개발형태 및 입지에 따른 분류 = 24
4. 개발방식에 따른 외국의 항만 워터프런트 개발 = 27
제3절 항만친수공간의 개발배경 및 시설 = 28
1. 친수공간의 일반적 개념 = 28
2. 법·제도적인 측면에서의 우리나라의 친수공간 = 31
3. 항만친수공간의 의의 및 개발 배경 = 33
4. 항만친수공간의 시설유형 및 건설되는 시설 = 38
제3장 외국의 항만친수공간 개발사례 = 45
제1절 외국의 항만친수공간 개발유형 = 47
1. 보전 = 47
2. 재개발 = 48
3. 신개발 = 49
제2절 외국의 항만친수공간 개발사례 연구 = 50
1. 미국의 항만친수공간 개발사례 = 51
2. 일본의 항만친수공간 개발사례 = 60
3. 유럽의 항만친수공간 개발사례 = 70
제4장 우리나라 항만친수공간 개발계획 = 78
제1절 우리나라 항만개발 정책 = 79
1. 우리나라 항만 현황 = 79
2. 항만개발투자 현황 및 계획 = 81
제2절 우리나라 항만친수공간 확보계획 = 83
1. 항만친수공간 현황 = 83
2. 항만친수공간 투자계획 = 84
3. 유형별 항만친수공간 개발계획 = 86
제3절 항만별 친수공간의 개발계획 = 89
1. 부산항 = 90
2. 인천항 = 105
3. 기타 항만별 개발계획 = 113
제4절 항만친수공간 개발과제 및 발전방향 = 127
1. 항만친수공간 개발과제 = 127
2. 항만친수공간 발전방향 = 134
제5장 결론 = 14
Performance Evaluation of Space-Time Codes Applying OFDM in Mobile Wireless Communicaton
Get PDFRecently the rapid growth of wireless voice subscribers, the growth of the internet and the increasing use of portable computing devices suggest that wireless internet access will rise rapidly over the next few years. Wireless internet is demanded to increase the channel capacity and data rate. It is difficult to increase the channel capacity or reducing the effective error rate in a multipaths fading channel.
To solve the above problems in wireless communications, Tarokh et al. introduced space -time codes adopting a joint design of coding, modulation, and transmit diversity. Space-time coding introduces temporal and spatial correlation into signals transmitted from different antennas, in order to provide diversity at the receiver, and coding gain over an uncoded system without sacrificing the bandwidth. The spatial-temporal structure of these codes can be exploited to increase further the capacity of wireless systems with a relatively simple receiver structure. Simulation results show that at the frame error rate of the 32-state code with two receiver antennas gives about 3dB gain over the use of a 4 states and two receiver antennas with the 32-state code give about 6 dB gain over the use of one receiver antenna. It appears from the simulation results that the coding advantage obtained by increasing the number of states and diversity gain obtained by increasing the number of receive antenna.
This thesis also studies space-time codes applying orthogonal frequency division multiplexing (OFDM) systems in wireless communication. In OFDM, the entire channel is divided into many narrow parallel subchannels, thereby increasing the symbol duration and reducing or eliminating the intersymbol interference (ISI) caused by the multipath environments. At the frame error rate of 10^-1 the 32-state code with space-time codes applying OFDM gives about 7dB gain over the use of the 4-state code by simulation. Therefore, space-time codes applying OFDM systems can be used for highly efficient data transmission over mobile wireless channels.목차
Nomenclature = ii
Abstract = iii
제1장 서론 = 1
제2장 시공간 부호의 부복호 방식 = 3
2.1 시공간 부호의 기본 개념 = 3
2.2 시공간 트렐리스 부호 = 11
2.3 시공간 블록 부호 = 17
제3장 시공간 부호를 적용한 OFDM 시스템 = 24
3.1 시공간 트렐리스 부호의 복호 방식 제안 = 24
3.2 OFDM 기본 원리 및 시스템 구성 = 27
3.3 OFDM을 적용한 시공간 트렐리스 부호 = 30
3.4 OFDM을 적용한 시공간 블록 부호 = 32
제4장 시뮬레이션에 의한 시공간 부호의 성능 분석 = 34
4.1 OFDM을 적용하지 않은 경우 = 34
4.2 OFDM을 적용한 경우 = 37
제5장 결론 = 39
참고문헌 = 4
(The) Optimal Design of Laterally Tilted SCH-SLD with Window Region
Get PDFIn this study, It was proposed laterally-tilted SCH(Separate Confinement Heterostrucure)-SLD(Superluminescent Laser Diode) with a window region in order to apply to the fiber optic sensing systems, such as Mach-Zehnder fiber optic interferometer and fiber optic gyroscope(FOG). Theoretical analyses have been tried to design high power and stable operating SLD, especially, the SLD operating at 1.55㎛ wavelength range which is the lowest absorption wavelength in silica(SiO2) optical fiber. Therefore the materials and structures of active layer and SCH layer were chosen as conventional In_(1-x)Ga_x As_y P_(1-y) quaternary composition systems.
From the transverse mode and lateral mode analyses of waveguide, the optical power distributions and the optical confinement factor have been studied for single-mode high power operation. According to these analyses, it was calculated SCH layer composition and the thickness to obtain the maximum optical confinement factor.
For the stable superluminescent operation, the facet reflectivity of SLD has to be lowered than 10^-4. The AR coating condition has been investigated with three kinds of TiO₂/SiO₂ structures, such as single layer, one pair layer, and multiple layers.
Furthermore, in order to find to easy way to fabricate low values of reflectivity, several cases, such as using unpumped window region effects or tilted facet including above AR coating results, respectively, were calculated with the gaussian beam approximation and mode analysis.
From these researches, it was confirmed that several results to fabricate the efficient and stable SLD.
In case of using 1.3㎛ InGaAsP SCH composition layer, the layer thickness was obtained 0.08㎛ to get the maximum optical confinement factor.
In case of single layer coating, such as TiO₂ and SiO₂, to get the minimum reflectivity at 1.55㎛ wavelength, each layer thickness was obtained 1790Å, 2690Å respectively. And in case of TiO₂/SiO₂ one pair layer, to get below 1% reflectivity in AR coating, TiO₂, SiO₂ thickness is 1500∼2000Å, 1100∼1700Å respectively. And in case of TiO₂/SiO₂ multiple layers, the reflectivity was higher than other cases.
In case of using 0.2㎛ active layer thickness, 0.08㎛ SCH layer thickness, window region length is 100㎛ in without AR coating, 10㎛ in 1% AR coating to obtain about 10^-4 reflectivity. When the tilted angle is about 10∼15。, reflectivity is about 10^-3.
From these results, it was confirmed that it is possible to fabricate the stable SLD without AR coating analytically, if the window region length and tilted angle were controlled appropriately in given device structure.ABSTRACT = ⅲ
제 1 장 서론 = 1
1-1 광산업의 현황 = 1
1-2 본 논문의 배경 및 목적 = 2
1-3 본 논문의 구성 = 4
참고문헌 = 6
제 2 장 SCH-SLD의 모드 해석 = 10
2-1 SCH-SLD의 모델링 = 11
2-2 횡모드 해석 = 14
2-3 측모드 해석 = 22
2-4 결과 및 검토 = 31
참고문헌 = 32
제 3 장 SLD 무반사 코팅막의 설계 = 37
3-1 무반사 코팅을 위한 SLD모델링 = 38
3-2 무반사 코팅 박막에 대한 수치해석 = 43
3-4 결과 및 검토 = 50
참고문헌 = 51
제 4 장 SCH-SLD의 구조에 의한 반사도 = 54
4-1 윈도우영역에 의한 실효반사도 = 55
4-2 laterally tilted angle에 의한 실효반사도 = 62
4-3 결과 및 검토 = 68
참고문헌 = 69
제 5 장 결론 = 7
Biological Treatment of High concentrated Nitrogen Wastewater with Heavy Metals
Get PDFHeavy metal pollution problems have became one of the most important environmental issues in Korea. This is because the metal contaminants can cause serious toxic effects in biota in aquatic and soil environments. Metal plating wastewater has been usually treated by the physico-chemical methods such as chemical precipitation, reverse osmosis and evaporation. Characteristics of the wastewater, however, became increasingly complicated as the industry developed and combined treatment of the wastewater for the small scale factories became more common. Treatment of metal plating wastewater requires more effective technologie in terms of performance and economics that would be applied to the small scale metal industries
The long term goal of this study was to develop a metal plating wastewater treatment system that can be practically employed for the small scale metal industries. The specific aims of this study were : 1) to find and optimize the growth conditions of sulfate reducing bacterial consortia for an efficient removal, 2) to develop an anaerobic process packed with a floating granular media, 3) to develop a simultaneous removal process of heavy metals and nitrogen utilizing sulfate reducing bacteria(SRB), sulfur denitrification bacteria(SDNB), and heterotrophic denitrification bacteria(DNB).
To find effective treatment conditions for the electroplating wastewater treatment by SRB, the bacteria activity, removal capacity of heavy metals, and possibility of nitrogen removal were investigated with respect to a wide range of COD/sulfate ratios in an anaerobic continuous reactor. During the start-up period when COD/sulfate ratios were gradually increased from 1.53 with the fixed COD concentration of 500 mg/L as glucose, successful sulfate reduction rate(above 95%) was achieved. Furthermore, in order to determine the activities of SRB at varying COD/sulfate ratios, influent COD concentrations were controlled to maintain COD/sulfate ratios at 0.18, 0.33, 0.5, 0.82, 1.2 after fixation of sulfate concentration of 2000 mg/L in the feed electroplating wastewater. At the relatively low values(0.18, 0.33) deficiency of organics in the feed affected the activity of SRB. Sulfate reduction efficiency was 61% and 59%, at the COD/sulfate ratio of 0.82 and 1.2, respectively. The further increase of the ratio did not appear to increase the reduction efficiency. Indicating sulfide inhibited the SRB's activity at the high COD/sulfate ratios. From the results, economic COD/sulfate ratio was determined to be 0.33 to reduce sulfate 2000 mg/L.
The amount of external carbon source supplied could be determined on the basis of heavy metal concentration in the wastewaters since sulfate reduction rate can be controlled by the external carbon. Heavy metals were effectively removed by SRB at above pH 6.4 regardless of metal species, but removal efficiency decreased dramatically at pH 5.4 to decrease of SRB activity caused by unfavorable pH condition. Consequently, at least, pH 5.4 or higher was necessary for the neutralization of electroplating wastewaters to maintain the stable activity of SRB.
In case of the heavy metal inhibition test in a nitrification reactor, the results of Phase 1 showed about 20% inhibition, and maximum inhibition up to 75% was observed at the later phase experiments. The removal possibility of ammonium nitrogen(400mg/L) in electroplating wastewaters was tested by utilizing a putative symbiotic relationship of three different microorganisms. Nitrates of high concentration effectively removed in a single anaerobic reactor containing alkalinity of 3000mg/L(as CaCO3) and COD of 1000 (mg/L) by the putative symbiotic relationship of SRB, SDNB, and DNB.
The results from this study will contribute to an understanding of biological removal mechanism of heavy metals and nitrogen in the electroplating wastewater and to development of this treatment technologies in the future
(A) Study on the InGaAsP/InP Wafer Growth for the Fabrication of SLDs
Get PDFSLDs are known as proper optical sources for the applications related to the optical measurements, since their properties are intermediate between those of the LEDs and LDs. And it is expected that the demand of SLDs will be largely increased with the progress of optical industries.
This study is a fundamental work for the fabrication of high-performance SLDs by LPE system and the aim is to grow InGaAsP/InP wafers for 1.55㎛ SLDs.
Before the wafer growth, both structures were approximated to five-layer slab waveguides then analyzed theoretically using the wave equations for the transverse mode and effective-index approximation in order to obtain the optimized conditions for the growth of high-efficiency epi-wafers.
On the basis of the results and the theory of InGaAsP/InP growth by LPE, the thickness of each epi-layer and growth variables were determined, then each epi-wafer was grown by vertical LPE system handmade in this laboratory.
In the growth of SCH-MQW wafers, it was confirmed that epi-layers were grown thickly compared with the result of theoretical analysis at present stage, thus it appeared that more research was to be carried out in the future in order to obtain InGaAsP epi-layers enough thin to have quantum size effect.
In the growth of SC-DH wafers with 1.3㎛ InGaAsP SC layers, we obtained the thickness nearly coincident with the results of theoretical analysis and good surface quality, when the growth temperature was 630℃, the cooling rate was 0.8℃/min, and single crystal InP was used as InP solute for two-phase method. It was also confirmed that the lasing wavelength of the wafer was 1.55㎛ as a result of the measurement of photoluminescence.
Therefore, It could be confirmed that the growth of 1.55㎛ InGaAsP/InP epi-wafers for SLDs was possible by LPE system.
It is also expected that the fabrication of high-performance SLDs will be possible if the optimized PBH structure is designed using this wafer and then the proper methods for reflectivity control are applied.Abstract
제1장 서론 = 1
1.1 연구 배경 및 목적 = 1
1.2 본 논문의 구성 = 3
제2장 SLD의 개요 = 4
2.1 SLD의 일반적 특성 = 4
2.2 SLD 제작시 고려사항 = 5
제3장 고출력 SLD 제작을 위한 에피웨이퍼의 구조 해석 = 13
3.1 SCH-MQW 구조의 모드 해석 = 14
3.2 SC-DH 구조의 모드 해석 = 24
제4장 1.55㎛ InGaAsP=InP wafer 성장 = 32
4.1 LPE에 의한 DH wafer 성장 이론 = 33
4.2 SCH-MQW 웨이퍼 성장 = 38
4.3 SC-DH 웨이퍼 성장 = 44
제5장 결론 = 53
참고문헌 = 5
A Study on the Adaptive Control System of an Induction Motor for an Air Compressor
Get PDFVector control of an induction motor has advantage of a quick torque response, and has been applied to various industrial applications.
In the design of a speed control system of induction motors, PI controller has been widely used because its structure is very simple. However, it is difficult to obtain robust and stable speed control characteristics because the gain of the controller can not be adjusted automatically when the load disturbance or system parameter change.
The motor used in a reciprocating air compressor experience abrupt load change by the movement of piston. So, its speed is fluctuated.
This study proposes a new adaptive control system with conventional vector controller for a reciprocating air compressor. The proposed system consists of a load torque observer and a feed-forward compensation using neural network to obtain a robust speed control characteristic. The observer is designed based on the Gopinath theory. And the neural estimator is consisted of two layers, and is used to provide a real-time adaptive estimation of motor dynamics. The LMS(Least Mean Square) algorithm which has widely been used is applied as the learning algorithm for this network to minimize the difference between the actual speed and the predicted value by the neural estimator.
To verify the effectiveness of this algorithm, a computer simulation and a experimental test are carried out on the basis of theoretical consideration.
From the experimental result, it is confirmed that the transient responses under the 1[atm] and 2[atm] condition are reduced 80[ms] and 50[ms] respectively compared with conventional method, and also steady state speed fluctuations are reduced 50 [rpm] and 80[rpm].목차
Abstract = ii
1. 서론 = 1
2. 유도전동기 벡터제어 = 3
2.1 벡터제어 = 3
2.2 좌표 변환 = 6
2.3 슬립주파수 계산 = 8
3. 공기압축기 = 12
3.1 공기압축기의 개요 = 12
3.2 피스톤 및 크랭크기구의 기기역학 = 13
4. 적응 제어기 설계 = 19
4.1 이산형 부하토크 관측기 = 20
4.2 신경망 추정기의 설계 = 25
5. 시뮬레이션 및 시스템 구현 = 31
5.1 시뮬레이션 = 31
5.2 시스템 구현 = 35
5.3 실험 및 결과검토 = 40
6. 결론 = 43
참고문헌 = 4
Development of a Graph Library Using the Relational Database
Get PDFThe graph provides a powerful methodology to solve a lot of real-world problems. There has been much research on graph representations and algorithms. But, there are still many difficulties to apply graphs to practical domains.
This paper proposes a graph library developed on the relational database. Graphs are represented in the form of relational tables and then saved in a database. Graph operations are coded in terms of database languages such as the SQL. Users of the graph library can efficiently manage a large amount of graph data. Furthermore, graphs saved in the database can be concurrently shared among many users. The proposed graph library will be useful to represent and solve real world problems efficiently.제 1 장 서론 = 1
1.1 연구배경 및 목적 = 1
1.2 관련연구 = 3
1.3 연구 내용 및 구성 = 5
제 2 장 그래프 이론 = 6
2.1 그래프 이론의 기본 개념 = 6
2.2 그래프 이론의 응용 = 8
제 3 장 그래프의 관계형 데이터베이스 설계 = 13
3.1 통합된 그래프 테이블 = 13
3.1.1 그래프 테이블의 구조 = 14
3.1.2 그래프 테이블의 적용 = 18
3.2 분리된 그래프 테이블 = 20
3.2.1 그래프 테이블의 구조 = 21
3.2.2 그래프 테이블의 적용 = 24
제 4 장 그래프 라이브러리 = 27
4.1 그래프 데이터베이스 생성 = 28
4.2 그래프 데이터베이스 연결 = 해제 라이브러리 = 28
4.3 그래프 생성 라이브러리 = 28
4.4 삽입 해제 라이브러리 = 29
4.5 갱신 라이브러리 = 30
4.6 검색 라이브러리 = 31
4.7 삭제 라이브러리 = 33
4.8 복구와 저장 라이브러리 = 34
제 5 장 그래프 라이브러리 = 35
5.1 그래프 라이브러리의 사용 예 = 35
5.2 개발된 그래프 라이？洹？리를 이용한 응용 프로그램 = 40
제 6 장 결론 및 향후 과제 = 42
참고 문헌 = 43
Appendix = 4
(A) Study on Sea Water Freezing Behavior in a Flow Field with Bubbly Flow
Get PDFOne of the most essential things to maintain our lives is water. Water consumption is rapidly increasing due to the exclusive overpopulation, industrial development and improvement of people's living standards. However, only 1% of water source is available for human being, so the ever-increasing scarcity of water is getting serious as time goes by.
Korea also will be no exception of this tendency and many researches have often proven how urgent Korea is water deficiency problem. In order to reduce this problem, we try to make the most water through building multi-functional dams, rainmaking and developing desalination system. Among those, desalination system is expected to be the most effective method because of its availability of seawater. It'll enable us to get water steady and readily. When we select particular kind of desalination system devices, that decision is mostly influenced by fresh water produce cost. In order words, its efficiency depends on whether we can achieve possible energy source easily or not.
As environmentally friendly means, many people are encouraged to use LNG (Liquefied Natural Gas) in Korea and many countries of the world. Amount of LNG consumption is currently heading higher. In general, LNG which is stored below -162℃ in super-liquid tank requires certain energy to gasify because it changed into the gaseous state with high pressure wasted cold energy when it is sent to each part in need. LNG loses lots of cold energy (850kJ/kg) during this process of absorbing heat.
To take advantage of this wasted cold energy, we are developing the systems such as producing the frozen food processing, dry ice, liquefied hydrogen, liquefied nitrogen and seawater freezing desalination. Therefore we'll mainly focus on the development of a seawater freezing desalination system and design technique using wasted cold energy necessary to freezing behavior of seawater. This study is intended to achieve qualitative and quantitative fundamental data with respect to it.
The device mainly consists of test section(transparent acryl rectangular duct), a brine loopvisualizing the flow in freezing part, etc.
After considering mean concentration of seawater measuring water and refined salt with digital balance and salinity meter, the operating fluid can function as 3.5wt% NaCl aqueous solution.
We operate brine loop using ethylene glycol 40% aqueous solution within the temperature of -21.12℃(eutectic point of seawater). Visualizing section using nylon12 tracer measures PIV with Argon-ion laser. After injecting -0.5℃ air into the test-section accompanied by flow field, investigated the flow appearance in around cooled parts by using the PIV system.
The experiments were carried out for a variety of parameter, such as sea water velocity, air-bubble flow rate, and cooled part temperature. The shape of freezing layer, freezing rate and salinity of frozen layer were observed and measured. And the flow patterns around cooled parts were visualized using the PIV to analyze the relationship between the flow structure and the freezing characteristics. It was found that the experimental parameters gave a great influence on the freezing rate and the salinity of the frozen layermaintaining the temperature of cooled parts, PIV(Particle Image Velocimetry) systemAbstract = ⅲ
사용기호 = ⅵ
제 1 장 서론 = 1
1.1 연구의 배경 = 1
1.2 종래의 연구 = 11
제 2 장 실험방법 및 실험범위 = 15
2.1 실험방법 및 실험범위 = 15
2.2 PIV = 20
2.3 해수의 동결거동 = 22
제 3 장 냉각원관에서의 해수동결 = 24
3.1 실험장치 = 24
3.2 냉각원관의 열전달해석 = 28
3.3 냉각원관 주위의 해수동결거동 = 33
3.4 유속의 영향 = 38
3.5 공기 분사량의 영향 = 48
3.6 냉각면 온도의 영향 = 58
3.7 동결량의 무차원정리 = 68
3.8 결론 = 70
제 4 장 수？邰嗔？ 냉각평판에서의 해수동결 = 71
4.1 실험장치 = 71
4.2 수직평행 냉각평판의 열전달해석 = 75
4.3 수직평행 냉각평판 주위의 해수동결거동 = 79
4.4 유속의 영향 = 83
4.5 공기 분사량의 영향 = 93
4.6 냉각면 온도의 영향 = 103
4.7 동결량의 무차원정리 = 113
4.8 결론 = 115
제 5 장 총결론 = 116
참고문헌 = 118
맺음말 = 12
The Effect of Lubricant Containing Copper Alloy Nano-Powder on a Diesel Engine
Get PDFThe characteristic of a lubricant is very important when it is used under severe running condition.
Especially on diesel engines the better lubrication performance is required because of the extreme condition such as high temperature and pressure by combustion process in a cylinder.
Many researches work for improving a boundary lubrication performance have been executed by using solid lubricant but this general lubricant has not been applied to engine due to the extreme condition of high temperature and pressure in a cylinder.
Recently, the solid lubricant which contained a copper nickel alloy has been introduced and studied.
In this study, the author investigated the effects of lubricant which contains the copper nickel alloy nano-powder on a diesel engine performance.
The results were manifested to show the increase of maximum torque, and the decrease of cylinder pressure, exhaust gas temperature, scavenging air temperature, CO emission according to running time lapse at various speed and torque on a diesel engine.
It was assured that the lubricant which contains the copper nickel alloy nano-powder decreases friction and wear, and simultaneously increases the sealing effect in a cylinder on diesel engines.목차
Abstract = iii
제1장 서론 = 1
제2장 윤활유 및 첨가제 = 4
2.1 기관의 윤활 = 4
2.1.1 윤활상태 = 5
2.1.2 윤활유의 기능 = 6
2.1.3 윤활유의 조건 = 7
2.2 첨가제의 종류 = 8
2.3 첨가제의 특성 = 10
2.3.1 청정분산제 = 10
2.3.2 산화방지제 및 마모방지제 = 12
2.3.3 점도지수향상제 = 13
2.4 나노구리합금첨가 윤활제 = 15
제3장 실험장치 및 계측장치 = 17
3.1 실험장치 = 17
3.1.1 대상기관 = 17
3.1.2 냉각계통 = 21
3.2 계측장치 = 22
3.2.1 동력측정장치 = 24
3.2.2 배기가스분석기 = 26
3.2.3 실린더내 압력검출장치 = 28
3.2.4 연료소비율 측정장치 = 30
제4장 실험결과 및 고찰 = 31
4.1 최대토크 = 32
4.2 실린더내 연소 최고압력 = 33
4.3 연료소비율 = 38
4.4 배기가스온도 = 42
4.5 급기온도 = 45
4.6 배기배출물 = 48
4.6.1 NOx의 배출농도 = 48
4.6.2 CO의 배출농도 = 51
4.6.3 O₂의 농도 = 55
4.6.4 스모크의 배출농도 = 58
제5장 결론 = 61
참고문헌 = 6