With recent development of 3D printing technology, its applications to the bio-industry are increasing. Many research studies are being done for manufacturing personalized tablets through this technology in the pharmaceutical process. In this study, to control the dissolution rate of tablets, a lattice structure was inserted into the tablet and the dissolution rate was compared. The tablet proposed in this study can be manufactured by the FDM method, adopting a lattice structure with a large surface area-to-volume ratio. Tablets containing various lattice structures were fabricated using water-soluble PVA filaments and dissolution experiments were conducted in water at 37oC. As a result, it was confirmed that the specific surface area and the mass loss rate were proportional to both the 3D lattice structure and the monolith structure. Among different structures, the diamond structure had the most active dissolution.
In this paper, the relationship between various physical and chemical dynamics included in a gas cutting process was analyzed and a mathematical model was presented. To express the gas cutting process in a formula that could reflect the physics and chemical reaction dynamics, the entire process was classified into three stages: flame spurt, metal oxidation, and metal oxide melting. Flame spurt is caused by combustion of fuel gas and oxygen. It was modeled through fluid dynamics, chemical species transport, and reaction kinetics. Metal oxidation was modeled as a chemical reaction of surface oxidation and oxide growth based on temperature and concentration of species of the metal surface obtained through flame and cutting oxygen spurt results. Finally, the melting of metal oxide was expressed as a rate equation based on melting conditions, heat flux obtained in the previous two stages, and changed properties of the metal. The presented mathematical model could analyze dynamic relationships for each stage of a gas cutting process and connect them into one process. Results of this study can be used as basic data for future finite element analysis and simulations.
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A Comprehensive Review on Flame Scarfing of Steel Slabs: Fundamentals, Challenges, Evolution, and Future Jin Gao, Fengsheng Qi, Zhongqiu Liu, Sherman C. P. Cheung, Baokuan Li, Deqiang Li steel research international.2025;[Epub] CrossRef
The performance prediction and grain burn-back analysis of rocket motor are important steps in the designing of a solid propellant rocket motor. The grain burn-back analysis of the solid grain identifies the burning surface area at each burning step in order to predict pressure-time history of the rocket motor. In this study, the shape of propellant grains was conveniently designed based on a solid modeling program of conventional purpose and the internal ballistics analysis was performed using a Matlab code which was developed to analyze the grain burn-back for this shape model. Upon carrying several analyses for rocket motors, it was confirmed that the developed code is suitable and useful.
This paper reports the effectiveness of the introduction of NGDG-SOFC (Natural Gas-Fueled Distributed Generation Solid Oxide Fuel Cell) as a solution to social problems that could arise in the unification era due to the power shortage in North Korea. Under the actual operating conditions of the plant, a stack that operates at a voltage of 33.87 V and current of 31.24 A was modeled with a gross output of 1.06 kW and a net output of 1.00 kW considering the balance of plant (BOP) consumption power. Considering the average primary energy consumption in the ASEAN countries in 2020, 2,870 MW was estimated as the amount of power generation required in North Korea. Also, the gross area of the plant and the annual fuel cost were estimated. Consequently, it is concluded that the area of 861 km2 which corresponds to 0.71 percent of the gross area of North Korea, and fuel cost of about 1,474 million $/year are required. The introduction of NGDG-SOFC plants is believed to follow the global trend of renewable energy and resolving the power shortage in North Korea in an eco-friendly manner.
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Distributed generation parameter optimization method based on fuzzy C-means clustering under the Internet of Things architecture Xin Yao, Liyun Xing, Ping Xin Energy Reports.2021; 7: 106. CrossRef
Chemical mechanical planarization (CMP) is a wafer planarization process that uses chemical reactions initiated by slurry and mechanical actions by pad asperity. The progression of CMP causes temperature deviation on the pad surface. Increase in process temperature results in increased material removal rate (MRR). So, pad temperature distribution is closely related to With-In Wafer Non-Uniformity (WIWNU). In this study, the pad temperature distribution is modelled from the energy perspective and slurry supply location is suggested to reduce temperature deviation. An energy supplying expression was created by setting the micro area and substituting the applied pressure, relative velocity, and process time. The energy and temperature distributions were observed as quite consistent and the temperature peak matched well with highest friction heat point (HFHP). Based on the model expression, the slurry injection position was set to the center of pad, the HFHP and wafer center, and change in temperature distribution was measured. A comparative analysis was carried out employing the existing method that uses multiple nozzles rather than single nozzles and the deviation was reduced by about 18.5% when slurry was supplied to the HFHP for a single nozzle and by 24.7% when the largest flow rate was supplied for multiple nozzles.
Chemical mechanical planarization (CMP) is a semiconductor process which is necessary for multi-layer interconnection structure. CMP pad is a consumable used in the process and with numerous asperities on the surface that wear out by the load applied from the contact with the wafer. Also, it has a patterned wafer, the step height is gradually removed by contact of the asperities with upper and lower layers. The contact state would be different according to the step height reduction. Likewise, depending on the pattern size at the specific step height, the maximum radius of the asperity curvature differs whether it reaches the down area. In this study, the height distribution of asperities was expressed as a function of time and asperity height taking into account the wear of asperities, and based on the Greenwood-Williamson theory, a mathematical model for material removal rate considering pattern size was derived. The consistency of the novel model is verified with the CMP experiment conducted using oxide patterned wafers, and the experimental data were compared with the residual step height using theoretical removal rate. The root mean square error of the step height reduction was 19.84 nm.
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Precision Engineering and Intelligent Technologies for Predictable CMP Somin Shin, Hyun Jun Ryu, Sanha Kim, Haedo Jeong, Hyunseop Lee International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2121. CrossRef
Despite the importance of the usage stage in life cycle assessment (LCA), there is a lack of comprehensive studies on the usage stage modeling. Based on the literature review, this paper establishes a general framework of the usage stage modeling by redefining existing models and proposing new models. The proposed computational framework can provide the overview of the current research as well as lead researchers and practitioners to consider proper modeling techniques. The framework includes the representative usage scenario method, usage context modeling, and time series usage modeling. Also, future research directions are suggested with the proposed computational framework.
In this study, a 10 kW horizontal-axis lift-type wind turbine is analyzed and verified. The three-bladed wind turbine is modeled and analyzed with FAST which is a multi-body dynamics code for a wind turbine. The turbine without any advanced over speed protection except an on/off control was simulated and experimentally verified. In the verification, the field test results were found to be well predicted by the simulation. Also, a side-furling system was proposed for the wind turbine without changing parameters of the current system much. From the dynamic simulation for verification, the furling system was found to work well up to 20 m/s with a modified torque control schedule. Although the proposed furling system could not be verified experimentally in the field, a similar 10 kW wind turbine whose experimental results are available in the literature was used for a verification. It was found from the simulation that the prediction from the simulation with the furling system was close to the experimental results in the literature.
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Development and Validation of Control Algorithm for Variable Speed Fixed Pitch Small Wind Turbine Donggeun Jeong, Taesu Jeon, Insu Paek, Deokjin Lim Energies.2023; 16(4): 2003. CrossRef
Chemical Mechanical Planarization (CMP) is an indispensable process of forming multilayer integrated circuit. However, it is necessary to understand the pattern in order to achieve global planarization. Material Removal Rate (MRR) depends on the pattern density in the actual CMP process and is required to predict the MRR according to density of the pattern. Based on the Preston equation (CMP governing equation), the MRR can be expressed as a product of pressure, relative velocity, and the Preston`s coefficient. Therefore, understanding of pressure distribution acting on the patterned wafer is essential. Pressure distribution depends on contact area between pad asperity and wafer surface. In this study, pressure distribution according to contact mode between asperity and wafer surface where step height exists was analyzed, and the planarization model presented. Finally, a comparison was done between the mathematical model and the experimental data, and the planarization model was verified.
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Planarization Modeling for Device Pattern with Geometric Characteristics of Pad Asperity Somin Shin, Dasol Lee, Seonho Jeong, Kyeongwoo Jeong, Jinuk Choi, Haedo Jeong Journal of the Korean Society for Precision Engineering.2020; 37(8): 567. CrossRef
Variation of Pad Temperature Distribution by Slurry Supply Conditions Jinuk Choi, Seonho Jeong, Kyeongwoo Jeong, Haedo Jeong Journal of the Korean Society for Precision Engineering.2020; 37(12): 873. CrossRef
In this paper, finite element modeling methods for cylindrical composite lattice structures were verified through natural frequency test. Finite element models for cylindrical composite lattice structure were developed using beam, shell and solid elements. Natural frequency test was measured using impact test method under free-boundary condition. The analysis result of the beam element model showed up to 23% errors because the beam element could not consider the degradation of mechanical properties of non-intersection parts of the composite lattice structures. On the other hand, the natural frequencies of finite element analysis for shell and solid element models showed good results with natural frequencies test. From the analysis of the experiment, finite element model for composite lattice structures should use shell or solid element which takes into consideration the intersection and non-intersection parts.
FEM (Finite Element Method)-based numerical analysis model, which is known as CAE (Computer Aided Engineering) technology, has been adopted for the visual/mechanical analysis of machining process. The essential models for the FEM analytical model are the plasticity model of workpieces, friction model, and wear rate model. Usually, the outputs of the FEM analytical model are the cutting force, the cutting temperature, and chip formation. Based on these outputs, the machining performance can be virtually evaluated without experiments. Nowadays, there are emerging machining technologies, such as cryogenic assisted machining and CFRP machining. Therefore, FEM technique can be one of the good candidate to virtually evaluate emerging developed machining technologies.
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Post-machining Deformation Analysis for Virtual Machining of Thin Aluminium Alloy Parts Soo-Hyun Park, Eunseok Nam, Myeong Gu Gang, Byung-Kwon Min International Journal of Precision Engineering and Manufacturing.2019; 20(4): 687. CrossRef
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