• Journal of the Korean Society for Precision Engineering
• /
• v.28 no.2
• /
• pp.176-184
• /
• 2011

As modern megalopolises become more complex and huge, convenience and safety of citizens are main components for a welfare state. In order to make safe society, telemetrics technology, which remotely measures the information of target system using electronic devices, is an essential component. In general, telemetrics technology consists of USN (ubiquitous sensor network) based on a wireless network, smart sensor, and SoC (system on chip). In the smart sensor technology, the following two problems should be overcome. Firstly, because it is very difficult for transducer manufacturers to develop smart sensors that support all the existing network protocols, the smart sensor must be independent of the type of networking protocols. Secondly, smart sensors should be modular so that a faulty sensor element can be replaced without replacing healthy communication element. To solve these problems, this paper investigates the feasibility of an IEEE 1451 based ZigBee smart sensor system. More specifically, a smart sensor for large network coverage has been developed using ZigBee for active telemetrics.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.17 no.1
• /
• pp.70-79
• /
• 2013

In this work, a steady-state performance modeling and off-design performance analysis of the 2-spool separate-flow turbofan engine named (BR715-56) which is a power plant for the narrow body commercial aircraft is carried out for engine performance behaviors investigation and condition monitoring using a commercial code MATLAB/SIMULINK. Firstly, the engine component maps of fan, high pressure compressor, high pressure turbine and low pressure turbine are generated from similar component maps using the scaling method, and then the off-design performance simulation model is constructed by the mass flow matching and the work matching between components. The model is developed using SIMULINK, which has advantages of easy steady-stare and dynamic modelling and user friendly interface function. It is found that the off-design performance analysis results using the proposed model are well agreed with the performance analysis results by GASTURB at various operating conditions.

• Coupled systems mechanics
• /
• v.3 no.3
• /
• pp.305-318
• /
• 2014

The study deals with the physical modeling of a typical building frame resting on pile foundation and embedded in cohesive soil mass using complete three-dimensional finite element analysis. Two different pile groups comprising four piles ($2{\times}2$) and nine piles ($3{\times}3$) are considered. Further, three different pile diameters along with the various pile spacings are considered. The elements of the superstructure frame and those of the pile foundation are descretized using twenty-node isoparametric continuum elements. The interface between the pile and pile and soil is idealized using sixteen-node isoparametric surface elements. The current study is an improved version of finite element modeling for the soil elements compared to the one reported in the literature (Chore and Ingle 2008). The soil elements are discretized using eight-, nine- and twelve-node continuum elements. Both the elements of superstructure and substructure (i.e., foundation) including soil are assumed to remain in the elastic state at all the time. The interaction analysis is carried out using sub-structure approach in the parametric study. The total stress analysis is carried out considering the immediate behaviour of the soil. The effect of various parameters of the pile foundation such as spacing in a group and number piles in a group, along with pile diameter, is evaluated on the response of superstructure. The response includes the displacement at the top of the frame and bending moment in columns. The soil-structure interaction effect is found to increase displacement in the range of 58 -152% and increase the absolute maximum positive and negative moments in the column in the range of 14-15% and 26-28%, respectively. The effect of the soil- structure interaction is observed to be significant for the configuration of the pile groups and the soil considered in the present study.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.15 no.2
• /
• pp.167-173
• /
• 2015

Extraction of Finger-end points is one of the most process for user multi-commands in the Hand-Gesture interface technology. However, most of previous works use the geometric and morphological method for extracting a finger-end points. Therefore, this paper proposes the method of user finger-end points extraction that is motivated a ultrared diffused illumination, which is used for the user commands in the multi-touch display device. Proposed air-mouse is worked by the quantity state and moving direction of extracted finger-end points. Also, our system includes a basic mouse event, as well as the continuous command function for expending a user multi-gesture. In order to evaluate the performance of the our proposed method, after applying to the web browser application as a command device. As a result, the proposed method showed the average 90% success-rate for the various user-commands.

• Tribology and Lubricants
• /
• v.34 no.2
• /
• pp.49-54
• /
• 2018

Hydraulic reciprocating seal has been widely used to prevent fluid leakage in hydraulic systems. Also, hydraulic reciprocating seal plays a significant role to provide lubricant film at contacting interface to minimize tribological problems due to sliding with counter material. To predict lifetime of hydraulic reciprocating seal, quantitative understanding of wear characteristics with respect to operating conditions such as normal force and sliding speed is needed. In this work, effect of sliding speed on wear of polyurethane (PU) hydraulic reciprocating seal were experimentally investigated using a pin-on-disk tribo-tester. The wear characteristics of PU specimens were quantitatively determined by comparing the confocal microscope data before and after test. It was found that the wear rate of PU specimens decreased from $4.9{\times}10^{-11}mm^3$ to $1.1{\times}10^{-11}mm^3/Nm$ as sliding speed increased from 120 mm/s to 940 mm/s. Also, it was observed that the friction decreased slightly as the sliding speed increased. Improvement of lubrication state with increasing sliding speed was likely to be responsible for this enhanced friction and wear characteristics. This result also suggests that decrease in sliding distance between PU elastomer and counter materials at lower sliding speed is preferred. Furthermore, the quantitative assessment of wear characteristics of PU specimen may be useful in prediction of lifetime of PU hydraulic reciprocating seal if the allowed degree of wear for failure of the seal is provided.

• Journal of Welding and Joining
• /
• v.23 no.3
• /
• pp.61-67
• /
• 2005

Since lead (Pb)-free solders for electronics have higher melting points than that of eutectic Sn-Pb solder, they need higher soldering temperatures. In order to decrease the soldering temperature we tried to coat Sn-Bi layer on $Sn-3.5\%Ag$ solder by electroplating, which applies the mechanism of transient liquid phase bonding to soldering. During heating Bi will diffuse into the $Sn-3.5\%Ag$ solder and this results in decreasing soldering temperature. As bonding samples, the 1608 capacitor electroplated with Sn, and PCB, its surface was finished with electroless-plated Ni/Au, were selected. The $Sn-95.7\%Bi$ coated Sn-3.5Ag was supplied as a solder between the capacitor and PCB land. The samples were reflowed at $220^{\circ}C$, which was lower than that of normal reflow temperature, $240\~250^{\circ}C$, for the Pb-free. As experimental result, the joint of $Sn-95.7\%Bi$ coated Sn-3.5Ag showed high shear strength. In the as-reflowed state, the shear strength of the coated solder showed 58.8N, whereas those of commercial ones were 37.2N (Sn-37Pb), 31.4N (Sn-3Ag-0.5Cu), and 40.2N (Sn-8Zn-3Bi). After thermal shock of 1000 cycles between $-40^{\circ}C$ and $+125^{\circ}C$, shear strength of the coated solder showed 56.8N, whereas the previous commercial solders were in the range of 32.3N and 45.1N. As the microstructures, in the solder $Ag_3Sn$ intermetallic compound (IMC), and along the bonded interface $Ni_3Sn_4$ IMC were observed.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.5 no.2
• /
• pp.109-121
• /
• 1995

Reaction coulples of SiC with cobalt were annealed in an Ar/4 vol% $H_2$ atmosphere at temperatures between $950^{\circ}C$ and $1250^{\circ}C$for various times between 4 and 100 h. At temperatures above $950^{\circ}C$, solid state reactions lead to the formation of various silicides with carbon precipitates. The typical reaction layer sequence was $SiC/CoSi + C/CozSi + C/CozSi/CozSi + C/{\cdot\cdot\}/CO_2Si/CO$ in the reaction zone. The mechanism of the periodic band structure formation with the carbon precipitation behaviour was examined and discussed in terms of reaction kinetics and thermodynamic considerations. The growth of the reaction zone has a square root of time dependence. The reaction kinetics is proposed to estimate the effective reaction constant from the parabolic gowth of the reaction zone. The mechanical properties of the reaction zones were determined by the microhardness test.

• Korean journal of communication and information
• /
• v.74
• /
• pp.72-108
• /
• 2015

The more mobile technology evolves, the more users are trapped in mobile technology by being encouraging the replacement with state-of-the-art technology. However, the use of device is not entirely determined by technology's attributes itself. The meaning of smartness can be varied by 'how users accept and perceive immediate spatial perception from reality to mobile space' without recognizing the boundaries between them. This study focuses on the analysis of 'smart usage' for smartphone and this is verified the concept of 'smart usage' by the second-order measurement model. The result show that the concept organization of 'smart usage' had been differentiated and elicited by the six factors - 'multifunctional use readiness', 'administrative efficiency', 'embedded media', 'device connectivity', 'user-friendly optimization', and 'external connectivity(being connected). According to the conceptual factors, 'smart usage' can be explained in an individual's autonomous ability to control a mobile interface and to utilize a wide range of applications of smartphones.

• Journal of the Institute of Electronics Engineers of Korea SC
• /
• v.41 no.2
• /
• pp.9-16
• /
• 2004

As the industry is developed, uses of various electric motor are increasing from general home to various fields of industry, and the kind becomes various daily. For these reasons, it is required to study the remote control and a package management about change of a speed drive system the supervision of administration appliance by real time, and the collection and process data together using internet prevailed on industry whole. Also, we can expect big effect in time and space, side of cost-cutting by control directly and manage appliance through internet. This paper deals with the development of a Web-Based remote control system for permanent magnet synchronous motor drives. The client/server system using TCP/IP protocols and DSP controller for remote control through internet and the Web interface that users can confirm data and state of PMSM is developed. This system is available for driving, braking, variable speed control and monitoring for PMSM in real time through administration program of Web-Based.

• The Journal of the Korea Contents Association
• /
• v.20 no.2
• /
• pp.594-606
• /
• 2020

On the contrary to the steady rise of social problems about depression, only a few take care of mental health themselves due to their negative perception of psychotherapy. In this study, we propose service design and user interface design of mobile applications that introduce an automatic emotional recognition system to prevent leaving depression unattended. First, we have come up with improvements in the usability of existing apps through literature research and case analysis, and draw out Personas from surveys and in-depth interviews of young people. As an essential element of the design of the Depression Improvement Service, we recommend having three components: writing a diary to manage schedule, recognize users' emotional state through avatar management, and tracking down emotional points to improve the cognitive system. Through this proposal, we want to prevent the development of depression and help to resolve the changes in perception of depression and longitude depression on our own. Ultimately, we publicize the necessity of mental health care application design and expect to lower the personal and social costs for psychiatric care.