• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.135-140
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• 2021

In this paper is a study on system design to prevent accidents using accelerometers. A switching power FET was configured at the power supply stage, and DC-DC converter, a regulator, and an LDO were designed for the power supply. In order to solve the power problem at once, it was divided into two parts, and a 3-axis accelerometer was designed to extract motion information to safely prevent accidents. Microprocessor enables communication through I2C and UART communication ports, and enables debugging through J-LINK. As a result of measuring the acceleration sensor data, it was confirmed that the power is normally cut off to prevent accidents when motion at an angle of 30° or more is detected.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.1
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• pp.91-96
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• 2014

KSLV-I (Korea Space Launch Vehicle-I) upper stage KM (Kick Motor) is a solid propulsion system which consists of igniter, SAD (Safety Arming Device), composite case, and submerged nozzle capable of TVC (Thrust Vector Control) actuation. Each subsystem of KM fulfilled development requirements for achieving a flight mission successfully. We confirmed the successful development of KM from the $3^{rd}$ flight test results of NARO on January 30, 2013. This article deals with the requirements of KM and the results on configuration management, mass variation, thrust axis alignment, and major test results and so on.

• Journal of the Korean Geophysical Society
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• v.7 no.1
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• pp.1-10
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• 2004

Gravity, magnetic and high-resolution seismic surveys were carried out in the Powell Basin to examine tectonic structure and recent sedimentation on Dec. 2002. The trend of negative gravity anomalies along the spreading axis of the Powell Basin changes from northwest to east-west toward south. Both boundaries of the basin with the Antarctic Peninsula and the South Orkey micro-continent show negative magnetic anomalies, which indicates that the boundaries were continental rift areas in the initial stage of spreading. Magnitude of the magnetic anomalies corresponding to the axis of the basin is rather small compared to those of normal spreading axises in other regions. Such small anomalies would be caused by reduction of magnetic strength of oceanic crust below thick sediments due to thermal alternation. High-resolution (3.5 kHz) seismic profiles reveal that top of the South Scotia Ridge is a flat terrain coverd with thin coarse sediments by glacial erosion. Thick oceanic sediments are deposited in the central part of the basin. Little deformation in the oceanic sediments indicates that the Powell Basin has been in stable tectonic environment after spreading of the basin stopped.

• Molecules and Cells
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• v.26 no.6
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• pp.576-582
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• 2008

Nervous system development takes place after positional information has been established along the dorsal-ventral (D/V) axis. The initial subdivision provided by a gradient of nuclear dorsal protein is maintained by the zygotic genes expressed along the D/V axis. In this study, an investigation was conducted to determine the range of Dpp function in repressing the expression of eagle (eg) that is present in intermediate neuroblasts defective (ind) and muscle specific homeobox (msh) gene domain. eg is expressed in neuroblast (NB) 2-4, 3-3 and 6-4 of the msh domain, and NB7-3 of the ind domain at the embryonic stage 11. In decapentaplegic (dpp) loss-of-function mutant embryos, eg was ectopically expressed in the dorsal region, while in dpp gain-of-function mutants produced by sog or sca-GAL4/UAS-dpp, eg was repressed by Dpp. It is worthy of note that Dpp produced from sim;;dpp embryos showed that Dpp could function at long range. However, Dpp produced from en-GAL4/UAS-dpp or wg-GAL4/UAS-dpp primarily acted at short-range. This result demonstrated that this discrepancy seems to be due to the repression of Dpp to EGFR signaling in sim;;dpp embryos. Taken together, these results suggest that Dpp signaling works at short-range, but can function indirectly at long-range by way of repression of EGFR signaling during embryonic neurogenesis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.603-606
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• 2000

This dissertation is concerned with ultra-precision profile measurement of aspheric surfaces using contact probing technique. A contact probe has been designed as a sensing device to obtain measuring resolutions in nanometer regime utilizing a leaf spring mechanism and a capacitive-type sensor. The contact probe is attached on the z-axis during measurement while aspheric objects are supported on an precision xy-stage whose lateral motions are monitored by a set of two orthogonal plane mirror type laser interferometers. Experimental results show that the contact probing technique developed in this investigation is capable of providing a repeatability of 50 nanometers with a $\pm$3$\sigma$ uncertainty of 300 nanometers. Thermal disturbance is found the most significant factor that should be precisely controlled for accurate measurement.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.377-382
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• 2005

This paper describes the design of micro machine tools system for mechanical machining of micro/meso scale mechanical parts. The micro machining systems such as $\mu-Late$, $\mu-milling/drilling$ machine and $\mu-grinding$ machine are the basic elements constructing $\mu-factory$ which gains more attention recently because of increasing needs of mico and nano-parts in various industrial and medical area. A miniaturized 3-axis milling machine with VCM stage and air spindle and palm-top size micro-late are designed, and air bearing stage and stepwise linear motion system with PZT are studied for motion system. The micro cutting characteristics are investigated experimentally, and reconfigurable machine structures are also considered.

• Journal of Biomedical Engineering Research
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• v.36 no.6
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• pp.271-275
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• 2015

The aim of this study was to develop a multi-nozzle based bioprinting system for fabrication of three-dimensional (3D) biological structure. In this study, a thermoplastic biomaterial that has relatively high mechanical stability, polycaprolactone (PCL) was used to make the 3D structure. A multi-nozzle bioprinting system was designed to dispense thermoplastic biomaterial and hydrogel simultaneously. The system that consists of 3-axes of x-y-z motion control stage and a compartment for injection syringe control mounted on the stage has been developed. Also, it has 1-axis actuator for position change of nozzle. The controllability of the printed line width with PCL was tested as a representative performance index.

• The Korean Journal of Zoology
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• v.27 no.3
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• pp.127-136
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• 1984

The specification of dorsal/ventral axis in the egg of Xenopus laevis was investigated as a series of oblique orientation to gravity by tilt and clinostat. The results are as follows. (1) If the eggs were oriented, in the early period after fertilization, to novel gravity by $15^\\circ, 30^\\circ, 45^\\circ$ and $60^\\circ$ tilt until gastrula stage, the site of involution was usually formed in the OpG side (the side opposing gravity). As the degree of tilt was raised from $15^\\circ to 60^\\circ$, the rate of relocation of the involution site was proportionally increased. (2) When UV-irradiated eggs were tilted period to first cleavage by $15^\\circ, 30^\\circ, 45^\\circ$ and $6\^\\circ$, the effect of UV syndrome was rescued, and the extent of rescue was propotional to the tilt degree. (3) The fertile eggs were loaded on the clinostats of several speeds. In the range of low speeds between $0.45 \\sim 9.0$ rph, the location of dorsal lip was dependent on the direction of rotation, and in $40 \\sim 360$ rph, lip was formed at a random position. In addition, some of the tadpoles experienced with clinostat showed the typical syndrome of "dorsal axis reduction". The above results were discussed regarding the mechanism of the establishment of dorsal/ventral palarity. palarity.

• Wind and Structures
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• v.17 no.6
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• pp.647-670
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• 2013

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k-${\varepsilon}$ turbulence model and the standard k-${\varepsilon}$ and k-${\omega}$ turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3-symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.927-934
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• 2002

The HANARO ( High-flux Advanced Neutron Application Reactor) has been operated since 1995. The Cold Neutron (CN) hole was implanted in the reflector tank from the design stage. Before a vacuum chamber and a moderator cell for the cold neutron source are installed into the CN hole, it is necessary to measure exactly the size of the inside diameter and thickness of the CN hole to prevent the interference problem. Due to inaccessibility and high radiation field in the CN hole, a mechanical measurement method is not permitted. The immersed ultrasonic technique is considered as the best way to measure the thickness and the diameter of the CN hole. The 4-Axis manipulator was designed and fabricated for locating the ultrasonic sensors. The transducer of an ultrasonic sensor having 10 MHz frequency leads to high resolution as much as 0.03mm. The inside diameter and thickness of 550 points of the CN hole were measured using 2 channel ultrasonic sensors. The results show that the thickness and inside diameter of the CN hole is in the range of 3.3∼6.7mm and 156∼ 165mm, respectively. This data will be a good reference for the design of the cold neutron source facility.