Design and Control of Flexure based XY θz Stage

Dongwoo. Kang,Kihyun Kim,Youngman Choi,Daegab Gweon,Sukwon Lee,Moongoo. Lee 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.11S

This article presents the design and control of an ultraprecision XY θz stage with nanometer accuracy. The stage has a plane mechanism and symmetric hexagonal structure which consists of a monolithic flexure hinge mechanism with three piezoelectric actuators and six flexures preserving the plane motion. The symmetric design reduces the effect of temperature gradient on the structure. Because the relationship between design variables and system parameters are quite complicated and there are some trade-offs among them, it is very difficult to set design variables manually and optimal design procedure is used. The objective of design is maximizing the 1st resonant frequency to improve the dynamic characteristics. The reason is that the stage must move with heavy load of about 20 ㎏. The higher resonant frequency also makes the stage stiffer and stronger against the dynamic force and moment. This paper describes the procedures of selecting parameters for the optimal design and a mathematical formulation for the optimization problem. The stage was designed to attain ± 10 um in the X- and Y-direction and ±90arcsec in the yaw direction at the same time and have the 1st resonant frequencies of 455.5 ㎐ in X- and Y-direction and 275.3 ㎐ for yaw direction without load. The stage was fabricated according to the optimal design results and experimental results indicate that the design procedure is effective. A conventional PI control results are presented for ultraprecision motion.

Heavy Metal Reduction and Solidification based on CO₂ Uptake using Hydroxide Solutions

( Dongwoo Kang ),( Juhee Son ),( Yunsung Yoo ),( Jinwon Park ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 한국폐기물자원순환학회 추계학술발표논문집 Vol.2019 No.-

A large amount of municipal solid waste (MSW) is produced daily due to the development of the industry and economy, most of which is utilized, incinerated, and deposited in landfills. In some developed nations in Europe, the utilization of MSW incineration (MSWI) ash as construction material has been studied because of its physical properties, which are similar to that of aggregate. Except for the utilization, most of the produced MSW is incinerated and deposited in landfills. However, landfills are not preferred in nations with confined land areas because they require a large area due to the MSW volume. To decrease the MSW volume, incineration can be used. However, problems occur with respect to the treatment of MSWI ashes. When MSWI ashes are buried, hazardous components, such as heavy metals and othermetal components, can leach out, resulting in groundwater pollution. Because the groundwater can flow over long distances, the environmental and biological problems are not limited to the land close to the landfill area. Hence, the MSWI ash must be stabilized. In this study, we discuss new methods that can be used to treat MSWI fly ashes withhigher heavy metal contents compared with MSWI bottom ashes. By adding 0.5 M ammonium, sodium, and potassium hydroxide solutions to the MSWI fly ash, the leaching of hazardous materials, including heavy metals and other metal cations, is induced. Subsequently, the characteristics of the solution, which has a high pH value, are utilized and a CO₂ uptake procedure is applied to fix the metal cations in the aqueous phase in solids for easier handling. Compared with conventional acid leaching, the heavy metals, which leach out of the MSWI fly ash, can be converted into solids by CO₂ uptake. Further handling is easier and additional wastewater processing is not required. To verify the methodology, the compositions of the untreated MSWI fly ash and MSWI fly ash treated with four types of leaching solution, that is, distilled water, 0.5 M sodium hydroxide aqueous solution, 0.5 M potassium hydroxide aqueous solution, and 0.5 M ammonium hydroxide solution, were analyzed. The heavy metal reduction characteristics were determined using supporting data obtained from different methods such as qualitative XRD and SEM analyses.

Carbon Dioxide Utilization using Industrial Wastewater Produced from Refined Salt Production Process

( Dongwoo Kang ),( Min-gu Lee ),( Hoyong Jo ),( Eunjung Kim ),( Jinwon Park ) 한국폐기물자원순환학회(구 한국폐기물학회) 2015 한국폐기물자원순환학회 3RINCs초록집 Vol.2015 No.-

In order to prevent climate changes caused by greenhouse gas emissions, researchers in many nations are struggle to reduce the amount of greenhouse gases contained in industrial flue gas. Among various greenhouse gases, carbon dioxide gas occupies large portion. So researches concerned with carbon dioxide reduction got many attentions. In this research, carbon capture and utilization and detailed methodology is dealt. Wastewater produced from refined salt production process was used as reactant in order to produce precipitated calcium carbonate salt which can be used as construction materials, additive in engineering plastic, pharmaceutical substances and so on.

Chemical Conversion of Carbon Dioxide via Aqueous Fixation using Divalent and Monovalent Metal Cations in Reject Brine Solutions

( Dongwoo Kang ),( Jinwon Park ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

In order to minimize the impact caused by global warming, the efforts to reduce the amount of carbon dioxide emission have been made for decades. There are various technologies in carbon reduction fields and usually they are called CCUS (Carbon Capture Utilization and Storage). In the CCUS technologies, carbon dioxide produced from various sources including power plants, industrial process are separated and processed. In CCS method, carbon dioxide is separated followed by compression and storage in the deep ocean or underground. However, to regenerate the absorbents, especially in wet absorption method, heat is essentially required to heat up the absorbents. To reduce this energy requirement problems and to enhance the economic feasibility of the whole process, the concept to make carbon dioxide into the reusable one has come arise. One of the most studied one is to make carbon dioxide into the metal carbonates by combining them with metal ions. However, securing metal cations are one of the problems. Some obtained its sources from natural minerals such as limestone. However, it seems not adequate to use resources to treat carbon dioxide, hence, we tried to use reject brine which have been produced from refined salt production facilities. In this process, natural seawater is drawn and sodium chloride is separated to make commercial salt product. And remaining solution is heated up to separate remaining salts. As a result, final solution becomes super-concentrated due to the evaporation of the solvent. When this reject brine is directly released to the near shore, it can trigger partial changes in concentration of near-ocean resulting in the negative impact in ecosystem. If divalent metal cations such as calcium or magnesium ions can be obtained in this reject brine solution, both securing sources and preventing environmental impact can be achieved at the same time. Herein, we developed a new carbon utilization method using calcium and magnesium cations dissolved in seawater-based industrial wastewater. Calcium and magnesium were separated in the form of hydroxide precipitate. Using 30 wt% aqueous monoethanolamine (MEA) solution, carbon dioxide was captured and reacted with the hydroxides to produce calcium carbonate and magnesium carbonate. After Ca²⁺ and Mg²⁺ separation, sodium chloride was used to produce sodium bicarbonate. The entire process produced 0.3819, 0.2549 and 0.4579 mol of calcium carbonate, magnesium carbonate and sodium bicarbonate, respectively. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were conducted to investigate their crystal structure. Moreover, FT-IR spectroscopy was utilized to investigate the ionic species under Na⁺-rich conditions.

Analysis of Electric Machine Charateristics for Robot Eyes Using Analytical Electromagnetic Field Computation Method

Dongwoo Kang,Ju Lee IEEE 2014 IEEE transactions on magnetics Vol.50 No.2

<P>This paper proposes an electromagnetic field computation method using an interpolation method with sigmoid functions. This method is useful for approximating and developing a 3-D electromagnetic field model. Particularly, the authors have been researching a spherical motor for a robotic eye. The spherical motor has a spherical air-gap unlike the radial air-gap motor or the axial air-gap motor. The spherical motor proposed in this paper realizes three degrees-of-freedom movements with only one motor. As the spherical motor has a complicated coil structure, the 3-D FEM would be essential for calculating torque while the rotor is tilted. However, 3-D FEM requires much computation time and a huge memory capacity to store the results. The electromagnetic field is rapidly calculated using an interpolation torque function proposed in this paper. The improvement of the spherical motor due to our method is verified through experiment, the results of which are compared with simulation data.</P>

Investigation on synchronization of the offset printing process for fine patterning and precision overlay

Kang, Dongwoo,Lee, Eonseok,Kim, Hyunchang,Choi, Young-Man,Lee, Seunghyun,Kim, Inyoung,Yoon, Dukkyun,Jo, Jeongdai,Kim, Bongmin,Lee, Taik-Min American Institute of Physics 2014 JOURNAL OF APPLIED PHYSICS - Vol.115 No.23

Offset printing processes are promising candidates for producing printed electronics due to their capacity for fine patterning and suitability for mass production. To print high-resolution patterns with good overlay using offset printing, the velocities of two contact surfaces, which ink is transferred between, should be synchronized perfectly. However, an exact velocity of the contact surfaces is unknown due to several imperfections, including tolerances, blanket swelling, and velocity ripple, which prevents the system from being operated in the synchronized condition. In this paper, a novel method of measurement based on the sticking model of friction force was proposed to determine the best synchronized condition, i.e., the condition in which the rate of synchronization error is minimized. It was verified by experiment that the friction force can accurately represent the rate of synchronization error. Based on the measurement results of the synchronization error, the allowable margin of synchronization error when printing high-resolution patterns was investigated experimentally using reverse offset printing. There is a region where the patterning performance is unchanged even though the synchronization error is varied, and this may be viewed as indirect evidence that printability performance is secured when there is no slip at the contact interface. To understand what happens at the contact surfaces during ink transfer, the deformation model of the blanket's surface was developed. The model estimates how much deformation on the blanket's surface can be borne by the synchronization error when there is no slip at the contact interface. In addition, the model shows that the synchronization error results in scale variation in the machine direction (MD), which means that the printing registration in the MD can be adjusted actively by controlling the synchronization if there is a sufficient margin of synchronization error to guarantee printability. The effect of synchronization on the printing registration was verified experimentally using gravure offset printing. The variations in synchronization result in the differences in the MD scale, and the measured MD scale matches exactly with the modeled MD scale. (C) 2014 AIP Publishing LLC.

Absorption characteristics of potassium carbonate-based solutions with rate promoters and corrosion inhibitors

Kang, Dongwoo,Lee, Min-Gu,Yoo, Yunsung,Park, Jinwon Springer-Verlag 2018 JOURNAL OF MATERIAL CYCLES AND WASTE MANAGEMENT Vol.20 No.3

Possibility of Carbon Dioxide Conversion Using Seawater through Aqueous Approach

Dongwoo Kang,Min-Gu Lee,Hyungbae Gil,Eunjung Kim,Jinwon Park 한국폐기물자원순환학회 2014 한국폐기물자원순환학회 학술대회 Vol.2014 No.11

The amount of carbon dioxide emission is continuously increasing and many researchers are concerned about climate change caused by its emission. Hence, some technologies which can reduce its emission have been developed and commercialized in many industries. These technologies are commonly called Carbon Capture and Storage (CCS) technology. In conventional CCS technology, carbon dioxide gas produced from industrial processes was usually captured by basic liquid absorbent such as monoethanolamine(MEA) and so on. After it is captured by those absorbents, they was flown to desorption step and was compressed at high pressure and transported to suitable places such as deep ocean or deep underground. However, there exist some problems when carbon dioxide is stored in such places. For instance, leak into the atmosphere can occur. Also, some nations including Korea may have difficulty finding suitable places for its storage since area of the nations is not that large and the ground is not stable. So, the method that can utilize captured carbon dioxide has been developed. When carbon dioxide is combined with metal cation such as calcium ion, it becomes calcium carbonate (CaCO3) which can be used for various purposes like construction materials, pharmaceutical manufacture, additives and so on. This is called Carbon Capture and Utilization (CCU) technology. In this research, seawater was used to supply calcium ions. There contained much amount of calcium component in seawater and amount of seawater is virtually limitless. MEA was used as absorbents and saturated by simulated flue gas. Pretreated seawater was then added to saturated absorbent. When carbon dioxide gas is dissolved to MEA, it exist in forms of ions and they can easily produce precipitated calcium carbonate (PCC) salts by reacting with calcium ions contained in seawater.

CO₂ Fixation and Utilization Based on Indirect Aqueous Carbonation

( Dongwoo Kang ),( Min-gu Lee ),( Yunsung Yoo ),( Jinwon Park ) 한국폐기물자원순환학회 2017 젊은 연구자 학술연구발표회 Vol.15 No.0

The Characteristics of Carbon Dioxide Absorption and Conversion into Metal Carbonate Salt via Indirect Aqueous Carbonation

( Dongwoo Kang ),( Min-gu Lee ),( Hoyong Jo ),( Jinwon Park ) 한국폐기물자원순환학회 2016 젊은 연구자 학술연구발표회 Vol.14 No.0