• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.418-418
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• 2008

The electrochemical etching of silicon in HF-based solutions is known to form various types of porous structures. Porous structures are generally classified into three categories according to pore sizes: micropore (below 2 nm in size), mesopore (2 ~ 50 nm), and macropore (above 50 nm). Recently, the formation of macropores has attracted increasing interest because of their promising characteristics for an wide scope of applications such as microelectromechanical systems (MEMS), chemical sensors, biotechnology, photonic crystals, and photovoltaic application. One of the promising applications of macropores is in the field of MEMS. Anisotropic etching is essential step for fabrication of MEMS. Conventional wet etching has advantages such as low processing cost and high throughput, but it is unsuitable to fabricate high-aspect-ratio structures with vertical sidewalls due to its inherent etching characteristics along certain crystal orientations. Reactive ion dry etching is another technique of anisotropic etching. This has excellent ability to fabricate high-aspect-ratio structures with vertical sidewalls and high accuracy. However, its high processing cost is one of the bottlenecks for widely successful commercialization of MEMS. In contrast, by using electrochemical etching method together with pre-patterning by lithographic step, regular macropore arrays with very high-aspect-ratio up to 250 can be obtained. The formed macropores have very smooth surface and side, unlike deep reactive ion etching where surfaces are damaged and wavy. Especially, to make vertical microwire or nanowire arrays (aspect ratio = over 1:100) on silicon wafer with top-down photolithography, it is very difficult to fabricate them with conventional dry etching. The electrochemical etching is the most proper candidate to do it. The pillar structures are demonstrated for n-type silicon and the formation mechanism is well explained, while such a experimental results are few for p-type silicon. In this report, In order to understand the roles played by the kinds of etching solution and mask patterns in the formation of microwire arrays, we have undertaken a systematic study of the solvent effects in mixtures of HF, dimethyl sulfoxide (DMSO), iso-propanol, and mixtures of HF with water on the structure formation on monocrystalline p-type silicon with a resistivity with 10 ~ 20 $\Omega{\cdot}cm$. The different morphological results are presented according to mask patterns and etching solutions.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.99-113
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• 2020

In the future, robots and drones for the convenience of our lives in everyday life will increase. As a method for controlling this, a remote control or a human voice method is most commonly used. However, the remote control needs to be operated by a person and can not ignore ambient noise in the case of voice. In this paper, we propose an economical attitude information acquisition method to accurately acquire the posture information of the arm in real time under the assumption that the surround drones or robots can be controlled wirelessly with the posture information of the arm. For this purpose, the extended Kalman filter was used to eliminate the noise of the arm position information. in order to detect the arm movement, a low cost MEMS type sensor was applied to secure the economical efficiency of the apparatus. To increase the wear ability of the arm, We developed a compact and lightweight attitude information acquisition system by integrating all functions into one chip as much as possible. As a result, the real-time performance of 1 ms was secured and the extended Kalman filter was applied to acquire the accurate attitude information of the arm with noise removed and display the attitude information of the arm in real time. This provides a basis for generating commands using real-time attitude information of the arm.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.149-153
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• 2005

The electron beam machining provides very high resolution up to nanometer scale, hence the E-beam writing technology is rapidly growing in MEMS and nano-engineering areas. In the optical column of the e-beam writer, there are several lenses condensing and focusing electron beams from electron gun with fringing magnetic fields. The polepieces of these lenses are usually made with high purity iron which is hard to fabricate and very expensive. In this paper, the possibility of using polepiece of object lens composed with pure iron and low carbon steel was examined to reduce cost. The magnetic field at object lens was calculated with finite element method, and practical focusing qualities of SEM pictures were observed comparing for the object lens polepieces with pure iron and two type of composed with low carbon steel.

• Journal of Sensor Science and Technology
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• v.27 no.3
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• pp.170-174
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• 2018

In this paper, the $TiO_2$/glucose oxidase (GOD) mixture has synthesized through simple and low-cost fabrication methods. The physical properties of the mixture were proved using an FT-IR/NIR spectrometer, an X-Ray diffractometer, and a Raman spectrometer. GOD maintained its bioactivity during all fabrication process. The current characteristics of the glucose biosensor were proportional to the glucose concentration and effective surface area of square pyramid on a silicon substrate. The maximum current change was measured in a pH 7.0 buffer solution. The simple and low-cost fabrication process and surface treatment can be used widely in previous research for improvements in effective surface area.

• Transactions of Materials Processing
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• v.15 no.4 s.85
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• pp.304-310
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• 2006

Due to a recent growth of the area of MEMS and a trend moving toward smaller scale, a micro manufacturing that is usually related with lithography is now emerging. Differently from traditional manufacturing processes, the micro or miniature manufacturing usually requires expensive sophisticated equipments and its characteristics are of high cost and of low productivity. However, a miniature stamping, which makes small sized product with a thin metal usually in the range of meso-scale, can be realized in a low cost and in a high productivity with relatively inexpensive equipments. For a successful development of miniature stamping, lots of obstacles, including material properties related with formability, have to be overcome. Since the thin metal shows distinctive characteristics, e.g., size effect and statistically scattered material properties, the formability of miniature stamping is not good in general and the possible shape with the miniature stamping is limited relatively simple shapes. Since the optimal blank improves formability and the improved formability can make up for problems of material properties, the possibility of success can be increased. This study is carried out to show the possibility of miniature stamping and to verify the effect of optimal blank for the miniature stamping.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1343-1351
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• 2014

Recent technological advances in wireless networks and microelectromechanical systems (MEMS) have led to the development of different types of mini-UAVs and their utilizations in various ways. This study endeavors to develop a low-cost mini-UAV with autonomous flight capability, in order to obtain geospatial information of a small or medium-sized area, and also assess its flight stability by comparing the predetermined flight paths against the actual flight paths. Based on a post-development flight test, stable flight has been proven achievable as follows: the maximum endurance speed is 1 hour, the flying distance is 50km, the horizontal accuracy of flight paths is about ${\pm}6{\sim}8m$, and the altitude accuracy is about ${\pm}8m$. Therefore, it is deemed that high-resolution images which can be utilized for geospatial information are obtainable. This indicates that a UAV flying at an altitude of 200m can acquire images across a $2km{\times}3km$ area on the ground within 25 minutes, which validates its high usability for obtaining high-solution images at low altitudes in the future.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.1
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• pp.73-76
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• 2010

The issue of inspection and characterization of microstructures has emerged as a major consideration in design, fabrication, and detection of MEMS devices. However, the conventional measurement techniques, including scanning electron microscopy (SEM) imaging, atomic force microscopy (AFM) scanning, and mechanical surface profiler, require often destructive process or may be difficult to measure with a wafer scale. In this paper, we characterize the surface profiles of microstructures using an optical scanner based on a DVD pick-up module. Scanning images of the microstructures are successfully generated using the intensity of reflected light from different depths of the surface profiles, based on the focus error signal (FES) from photodiodes. It is shown that the proposed optical scanner can be used as an alternative measurement system with high performance and low cost, compared to conventional measurement techniques.

• Current Research on Agriculture and Life Sciences
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• v.32 no.2
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• pp.79-84
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• 2014

The precision aerial application of agricultural unmanned helicopters has become a new paradigm for small farms with orchards, paddy, and upland fields. The needs of agricultural applications require easy and affordable control systems. Recent developments of MEMS technology based on inertial sensors and high speed DSP have enabled the fabrication of low-cost attitude system. Therefore, this study evaluates inertial MEMS sensors for estimating the attitude of an agricultural unmanned helicopter. The accuracies and errors of gyro and acceleration sensors were verified using a pendulum system. The true motion values were calculated using a theoretical estimation and absolute encoder measurement of the pendulum, and then the sensor output was compared with reference values. When comparing the sensor measurements and true values, the errors were determined to be 4.32~5.72%, 3.53~6.74%, and 3.91~4.16% for the gyro rate and x-, z- accelerations, respectively. Thus, the measurement results confirmed that the inertial sensors are effective for establishing an attitude and heading reference system (AHRES). The sensors would be constructed in gimbals for the estimating and proving attitude measurements in the following paper.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.12
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• pp.2563-2567
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• 2011

Advances in smart sensors, embedded systems, low-power design, ad-hoc networks and MEMS have allowed the development of low-cost small sensor nodes with computation and wireless communication capabilities that can form distributed wireless sensor networks. Time information and time synchronization are fundamental building blocks in wireless sensor networks since many sensor network applications need time information for object tracking, consistent state updates, duplicate detection and temporal order delivery. Various time synchronization protocols have been proposed for sensor networks because of the characteristics of sensor networks which have limited computing power and resources. However, none of these protocols have been designed with time representation scheme in mind. Global time format such as UTC TOD (Universal Time Coordinated, Time Of Day) is very useful in sensor network applications. In this paper we propose network time protocol extension for global time presentation in wireless sensor networks.

• Journal of Sensor Science and Technology
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• v.26 no.4
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• pp.235-238
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• 2017

In this study, the design of a tri-axis micromachined gyroscope is proposed and the vibration characteristic of the structure is analyzed. Tri-axis vibratory gyroscopes that utilize Coriolis effect are the most commonly used micromachined inertial sensors because of their advantages, such as low cost, small packaging size, and low power consumption. The proposed design is a single structure with four proof masses, which are coupled to their adjacent ones. The coupling springs of the proof masses orthogonally transfer the driving vibrational motion. The resonant frequencies of the gyroscope are analyzed by finite element method (FEM) simulation. The suspension beam spring design of proof masses limits the resonance frequencies of four modes, viz., drive mode, pitch, roll and yaw sensing mode in the range of 110 Hz near 21 kHz, 21173 Hz, 21239 Hz, 21244 Hz, and 21280 Hz, respectively. The unwanted modes are separated from the drive and sense modes by more than 700 Hz. Thereafter the drive and the sense mode vibrations are calculated and simulated to confirm the driving feasibility and estimate the sensitivity of the gyroscope. The cross-axis sensitivities caused by driving motion are 1.5 deg/s for both x- and y-axis, and 0.2 deg/s for z-axis.