• Journal of Ship and Ocean Technology
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• v.7 no.2
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• pp.29-39
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• 2003

A Coanda foil is a high-lift generating device exploiting the phenomena that flow separation is delayed if a high-speed jet is applied tangential to the surface as well known to the aerodynamic fields. In the present study, a Coanda foil with a flap is investigated to seek the possibility of marine application. Model experiments are carried out both in a towing tank and cavitation tunnel and surface pressure distributions, forces and moments acting on the foil are measured at the various angle of attacks and flap angles. The results are also compared to the numerical ones to show good agreements. The results of the present study demonstrate the practical applicability of the Coanda foil in the design of ship control surfaces.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.299-304
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• 2005

This paper describes the conceptual of device attached to rotary type sliding door system satisfying customer's reguirements. The TRIZ (Russian theory of Inventive Problem Solving) and Axiomatic Design methods are used for generating new ideas at the conceptual design stage efficiently. The ideas will be implemented in real products.

• Biomolecules & Therapeutics
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• v.26 no.4
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• pp.380-388
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• 2018

Neural stem cells (NSCs) have the ability to self-renew and differentiate into multiple nervous system cell types. During embryonic development, the concentrations of soluble biological molecules have a critical role in controlling cell proliferation, migration, differentiation and apoptosis. In an effort to find optimal culture conditions for the generation of desired cell types in vitro, we used a microfluidic chip-generated growth factor gradient system. In the current study, NSCs in the microfluidic device remained healthy during the entire period of cell culture, and proliferated and differentiated in response to the concentration gradient of growth factors (epithermal growth factor and basic fibroblast growth factor). We also showed that overexpression of ASCL1 in NSCs increased neuronal differentiation depending on the concentration gradient of growth factors generated in the microfluidic gradient chip. The microfluidic system allowed us to study concentration-dependent effects of growth factors within a single device, while a traditional system requires multiple independent cultures using fixed growth factor concentrations. Our study suggests that the microfluidic gradient-generating chip is a powerful tool for determining the optimal culture conditions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.1
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• pp.93-100
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• 2011

This paper presents a technical study for the first short stroke lightning current generator using a crowbar device. The so-called crowbar-technology is most common to make 10/350[${\mu}s$] impulse currents with high amplitude, and the lightning current generator with crowbar device has an economic advantage than the nominal RLC current generator. But both the operating efficiency and the operating reliability of crowbar spark gap are very important to design the current generator. So, the peaking circuit which consists of small capacitors and a spark gap is applied. And the multi-step coil for controlling the circuit constant at the different test conditions is used. The presented test facility is designed to perform impulse tests with amplitudes up to 50[kA] of 10/350[${\mu}s$].

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.8
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• pp.783-789
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• 2007

In this paper, firstly, we propose a generating method of the 3-D obstacle map using ultrasonic sensors. Secondly, we try to find the necessary stimulation conditions of compact tactile display device for effective transfer of obstacle information. The final goal of this research is the development of a walking guide system for the blind to walk safely. The walking guide system consists of a guide vehicle for the obstacle detection and a tactile display device for the transfer of the obstacle information. The guide vehicle, located in front of the walking blind, detects the obstacle using ultrasonic sensors. The processed information makes an obstacle map and transmits safe path and emergency situation to the blind by the tactile display. The tactile display device, located in the handle which is connected with the guide vehicle by cane, offers the processed obstacle information such as position, size, moving, shape of obstacle and safe path, etc. The concept of a walking guide system with tactile display is introduced, and experiments of 3-D obstacle detection and tactile perception are carried out and analyzed.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.846-864
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• 2017

Software Defined Network (SDN) realizes management and control over the underlying forwarding device, along with acquisition and analysis of network topology and flow characters through south bridge protocol. Data path Identification (DPID) is the unique identity for managing the underlying device, so forged DPID can be used to attack the link of underlying forwarding devices, as well as carry out DoS over the upper-level controller. This paper proposes a dynamic defense method based on Client-Puzzle model, in which the controller achieves dynamic management over requests from forwarding devices through generating questions with multi-level difficulty. This method can rapidly reduce network load, and at the same time separate attack flow from legal flow, enabling the controller to provide continuous service for legal visit. We conduct experiments on open-source SDN controllers like Fluid and Ryu, the result of which verifies feasibility of this defense method. The experimental result also shows that when cost of controller and forwarding device increases by about 2%-5%, the cost of attacker's CPU increases by near 90%, which greatly raises the attack difficulty for attackers.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.5
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• pp.299-304
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• 2018

An ideal circuit breaker should supply electric power to loads without losses in a conduction state and completely isolate the load from the power source by providing insulation strength in a break state. Fault current is relatively easy to break in an Alternating Current (AC) circuit breaker because the AC current becomes zero at every half cycle. However, fault current in DC circuit breaker (DCCB) should be reduced by generating a high arc voltage at the breaker contact point. Large fire may occur if the DCCB does not take sufficient arc voltage and allows the continuous flow of the arc fault current with high temperature. A semiconductor circuit breaker with a power electronic device has many advantages. These advantages include quick breaking time, lack of arc generation, and lower noise than mechanical circuit breakers. However, a large load capacity cannot be applied because of large conduction loss. An extinguishing technology of DCCB with polymeric positive temperature coefficient (PPTC) device is proposed and evaluated through experiments in this study to take advantage of low conduction loss of mechanical circuit breaker and arcless breaking characteristic of semiconductor devices.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.3
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• pp.265-268
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• 2011

In this paper, we designed and fabricated that fog alarm equipment detected to crew in maritime fog. Developed fog alarm equipment was combined sensor and a transmitter-receiver module using emitting device unit and receiver photoelectric element infrared LED using only the receive sensitivity was low, miniaturization. Experiment of the fabricated device had a standard that was humidity 70%, the fabricated one generating artificial-fog within visibility 1km. When humidity is over 70%, the fabricated one generates alarming sounds for a warning. When developed device apply to vessel will be able to respond quickly, according to dense fog in the accident.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.9
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• pp.1332-1347
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• 1993

Existing instruments are composed independently according to their function and user constructed instrumentation system with those instruments. But in the late 1980s VXI bus enables to construct instrumentation system with various modular type instruments. For an VXI bus system with the word serial protocol, an increase of data size can degrade the system performance. In this paper shared memory protocol is proposed to overcome performance degradation. The shared memory protocol is analyzed using the GSPN and compared with that of the word serial protocol. It is shown that the shared memory protocol has a better performance than the word serial protocol. The VXI bus message based-system with the proposed shared memory protocol is constructed and experimented with signal generating device and FFT analyzing device. Up to 80 KHz input signal the result of FFT analysis is accurate and that result is agree with that of conventional FFT analyzer. In signal generating experiment from 100 KHz to 1.1 GHz sine wave is generated.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.418-426
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• 2021

This study investigates the perception of radiation safety management in radiation generator manufacturing workers and medical institutions. The basic data obtained is further applied to improve active coping ability and safety levels. The knowledge and attitude practice score of radiation was found to be related to gender, age, marital status, occupation, position, current work period, total work period, radiation related work period, the manual available, defense facility maintenance, number of defense equipment, radiation safety education, special health examination, and recognition of radiation terms. In particular, the knowledge score of radiologists was highest among the radiation-related occupations (<0.05). Radiation safety management requires active defense endeavors to prevent radiation exposure, by both workers of radiation manufacturers and medical institutions. Moreover, institutional devices such as compliance with guidelines, periodic education, facility reinforcement, manual preparation, and special health checkups are required for efficient radiation safety management.