Hyo-Young Kim

Bio: Hyo-Young Kim is an academic researcher from KITECH. The author has contributed to research in topics: Voice coil & Vibration. The author has an hindex of 10, co-authored 37 publications receiving 327 citations. Previous affiliations of Hyo-Young Kim include Korea Polytechnic University & KAIST.

Development of a Nanoprecision 3-DOF Vertical Positioning System With a Flexure Hinge

Abstract: This paper describes the conceptual design of an ultraprecision 3-DOF (Z, Ox, Oy) vertical positioning system with nanometer precision. The vertical out-of-plane positioning system can be used for various nanoalignment applications, such as optical instrument alignment. The proposed vertical positioning system is driven by three piezoelectric (PZT) actuators and is guided by three rotationally symmetric hinges. Because the displacement generated by a PZT actuator is very small, the proposed system also includes an amplification hinge mechanism. Because the relationships between the variables of the hinge parameters and system performance levels are complicated, an optimization procedure to obtain optimal design parameters, which maximize the system bandwidth, is developed. Based on the solution to the optimization problem, the design of a vertical positioning system and finite-element-method simulation results are presented. Finally, the stage is manufactured and tested for verification. The stroke of the translational movement is 190 mm, and the stroke of the rotational movement is 0.5 mrad, whereas their in-position stability levels are ±2 nm and ±20 nrad and resolutions are 5 nm and 80 nrad, respectively. The settling time is less than 45 ms.

Optimal design and experiment of a three-axis out-of-plane nano positioning stage using a new compact bridge-type displacement amplifier

Abstract: This paper presents the development of a new compact three-axis compliant stage employing piezoelectric actuators and a new flexure structure. A proposed stage works out-of-plane (Z, θx, θy) direction. The stage consists of 4 amplification flexures mounted piezoelectric actuators. New structure of flexure reduces height and enhances dynamic performance of stage. To certify excellent performance of the stage, comparison accomplished between conventional amplification flexure and new compact bridge type flexure. Modeling and optimal design of new type nano positioning stage performed. The optimal design is executed on the geometric parameters of the proposed flexure structure using Sequential Quadratic Programming. Experiments are carried out to verify the static and dynamic performance of the stage. The proposed out-of-plane nano-positioning stage has a Z-directional motion range 190 μm and a θx, θy-directional motion range ±2 mrad. The resolution of the stage is 4 nm, 40 nrad, and 40 nrad in the Z-, θx-, and θy-directional motions, respectively. The size of stage is 150 × 150 × 30 mm3.

Development of a novel 3-degrees of freedom flexure based positioning system

Abstract: Flexure mechanisms have been widely used for nanometer positioning systems. This article presents a novel conceptual design of an ultra-precision 3-degrees of freedom (XYθ(Z)) positioning system with nanometer precision. The main purpose of this novel stage design is for the application of measurement equipment, in particular biological specimens. The stage was designed as a hollow type and with a compact size for the inverted microscope. This stage includes piezoelectric transducer actuators, double compound amplification mechanisms, moving plate, and capacitor sensors. The double compound amplification mechanism was designed using a mathematical model and analyzed by the finite element method. Since the relationship between the variables of the hinge parameters and system performances are complicated, an optimization procedure was used to obtain the optimal design parameters, which maximized the system bandwidth. Based on the solution of the optimization problem, the design of the stage and FEM simulation results are presented. Finally, the stage was manufactured and tested.

Development of a Novel Spherical Actuator With Two Degrees of Freedom

Abstract: This paper describes the design and implementation of a novel spherical actuator that can generate two tilt-motion degrees of freedom. Voice coil motors were adopted as actuators in a spherical actuator to utilize their simple driving principle and constant torque coefficient characteristic. The sensing and guiding mechanism was built inside the proposed spherical actuator and enabled compactness and ease of connection to other application systems. The actuator was designed using a design optimization framework to obtain high torque. A prototype actuator was manufactured with optimally designed parameters, and its performance was evaluated.

Design and Control of a 6-DOF Active Vibration Isolation System Using a Halbach Magnet Array

Abstract: Active vibration isolation systems (AVIS) reduce the vibrations transmitted to ultraprecision mechanical systems by providing managed stiffness and damping. Many types of AVIS are used in various fields. In nanoprecision measuring instrument fields, such as atomic force microscopy and scanning probe microscopy, the requirement for isolation of ground vibrations has always been of great interest to researchers. Bench-top-type six-degree-of-freedom (6-DOF) AVIS have been widely used in ultraprecision measuring applications. This paper describes the design, modeling, optimization, and validation of a new 6-DOF AVIS. The unique feature of the proposed system is its voice coil motor actuator that uses a Halbach magnet array to produce a high force constant. The results obtained using the proposed AVIS show that it can serve as a bench-top device for precision measuring machines.

Database Models And Managerial Intuition: 50% Model + 50% Manager

Abstract: We focus on ways of combining simple database models with managerial intuition. We present a model and method for isolating managerial intuition. For five different business forecasting situations, our results indicate that a combination of model and manager always outperforms either of these decision inputs in isolation, an average R2 increase of 0.09 (16%) above the best single decision input in cross-validated model analyses. We assess the validity of an equal weighting heuristic, 50% model + 50% manager, and then discuss why our results might differ from previous research on expert judgment.

Discrete Choice Experiments in Health Economics: Past, Present and Future

Abstract: Discrete choice experiments (DCEs) are increasingly advocated as a way to quantify preferences for health. However, increasing support does not necessarily result in increasing quality. Although specific reviews have been conducted in certain contexts, there exists no recent description of the general state of the science of health-related DCEs. The aim of this paper was to update prior reviews (1990–2012), to identify all health-related DCEs and to provide a description of trends, current practice and future challenges. A systematic literature review was conducted to identify health-related empirical DCEs published between 2013 and 2017. The search strategy and data extraction replicated prior reviews to allow the reporting of trends, although additional extraction fields were incorporated. Of the 7877 abstracts generated, 301 studies met the inclusion criteria and underwent data extraction. In general, the total number of DCEs per year continued to increase, with broader areas of application and increased geographic scope. Studies reported using more sophisticated designs (e.g. D-efficient) with associated software (e.g. Ngene). The trend towards using more sophisticated econometric models also continued. However, many studies presented sophisticated methods with insufficient detail. Qualitative research methods continued to be a popular approach for identifying attributes and levels. The use of empirical DCEs in health economics continues to grow. However, inadequate reporting of methodological details inhibits quality assessment. This may reduce decision-makers’ confidence in results and their ability to act on the findings. How and when to integrate health-related DCE outcomes into decision-making remains an important area for future research.

Mucinous colorectal adenocarcinoma: clinical pathology and treatment options.

Abstract: Mucinous colorectal adenocarcinoma is a distinct subtype of colorectal cancer (CRC) characterized by the presence of abundant extracellular mucin which accounts for at least 50% of the tumor volume. Mucinous colorectal adenocarcinoma is found in 10%–20% of CRC patients and occurs more commonly in female and younger patients. Moreover, mucinous colorectal adenocarcinoma is more frequently located in the proximal colon and diagnosed at an advanced stage. Based on its molecular context, mucinous colorectal adenocarcinoma is associated with the overexpression of mucin 2 (MUC2) and mucin 5AC (MUC5AC) proteins. At the same time, it shows higher mutation rates in the fundamental genes of the RAS/MAPK and PI3K/Akt/mTOR pathways. Mucinous colorectal adenocarcinoma also shows higher rates of microsatellite instability (MSI) than non-mucinous colorectal adenocarcinoma which might correlate it with Lynch syndrome and the CpG island methylator phenotype. The prognosis of mucinous colorectal adenocarcinoma as to non-mucinous colorectal adenocarcinoma is debatable. Further, the impaired responses of mucinous colorectal adenocarcinoma to palliative or adjuvant chemotherapy warrant more studies to be performed for a specialized treatment for these patients. In this review, we discuss the molecular background and histopathology of mucinous colorectal adenocarcinoma, and provide an update on its prognosis and therapeutics from recent literatures.

Enhanced mathematical modeling of the displacement amplification ratio for piezoelectric compliant mechanisms

Abstract: Piezo-actuated, flexure hinge-based compliant mechanisms have been frequently used in precision engineering in the last few decades. There have been a considerable number of publications on modeling the displacement amplification behavior of rhombus-type and bridge-type compliant mechanisms. However, due to an unclear geometric approximation and mechanical assumption between these two flexures, it is very difficult to obtain an exact description of the kinematic performance using previous analytical models, especially when the designed angle of the compliant mechanisms is small. Therefore, enhanced theoretical models of the displacement amplification ratio for rhombus-type and bridge-type compliant mechanisms are proposed to improve the prediction accuracy based on the distinct force analysis between these two flexures. The energy conservation law and the elastic beam theory are employed for modeling with consideration of the translational and rotational stiffness. Theoretical and finite elemental results show that the prediction errors of the displacement amplification ratio will be enlarged if the bridge-type flexure is simplified as a rhombic structure to perform mechanical modeling. More importantly, the proposed models exhibit better performance than the previous models, which is further verified by experiments.