• ETRI Journal
• /
• v.42 no.3
• /
• pp.341-350
• /
• 2020

In a wireless sensor network (WSN), the data transmission technique based on the cooperative multiple-input multiple-output (CMIMO) scheme reduces the energy consumption of sensor nodes quite effectively by utilizing the space-time block coding scheme. However, in networks with high node density, the scheme is ineffective due to the high degree of correlated data. Therefore, to enhance the energy efficiency in high node density WSNs, we implemented the distributed source coding (DSC) with the virtual multiple-input multiple-output (MIMO) data transmission technique in the WSNs. The DSC-MIMO first compresses redundant source data using the DSC and then sends it to a virtual MIMO link. The results reveal that, in the DSC-MIMO scheme, energy consumption is lower than that in the CMIMO technique; it is also lower in the DSC single-input single-output (SISO) scheme, compared to that in the SISO technique at various code rates, compression rates, and training overhead factors. The results also indicate that the energy consumption per bit is directly proportional to the velocity and training overhead factor in all the energy saving schemes.

• Solar Energy
• /
• v.18 no.3
• /
• pp.119-128
• /
• 1998

This study has been carried out to develop a thermo-diode system capable of adjusting heat flow direction, solar absorptivity and thermal capacity. What we call "Smart Module" here has emerged from a series of repeated processes involving design, construction and test. In all, it is found that liquid thermo-diode systems are viable in harnessing the sun's energy. The module can be applied for space heating in winter and reduce the cooling load of buildings in summer.

• Journal of the Korean Solar Energy Society
• /
• v.24 no.3
• /
• pp.93-100
• /
• 2004

This study aims to presents the applicability of economic measures for renewable energy The basic principle and method of economic analyses were investigated and total life cycle cost considering environmental costs according to $CO_2$ generation. In case study, adaptation of new small wind power system to buildings were proved to produce a profit if it is considered the environmental cost and increment of energy prices. And so the economic measures can be used not only for the investment decisions for economic analysis but also for the comparative analysis of environmental cost and economic profits.

• Advances in Energy Research
• /
• v.8 no.3
• /
• pp.145-153
• /
• 2022

Recent concerns about rising fuel prices and greenhouse gas emissions have focused attention on alternative energy sources, particularly in the transport sector. Transportation consumes 40% of overall fuel usage. As a result, a growing majority of researches on Electric Vehicles (EVs) and their Energy Management Systems (EMS) have been done. In order to enhance the performance and to meet the needs of drivers, more information regarding the EMS is needed. A new Energy Management System is proposed using a FOPID controller. To put the concept into practice, state equations are utilised. The fifth-order state-space model under study is a linked model with several inputs and outputs and the transfer matrices are calculated for decoupling the system. Utilizing these transfer matrices to decouple the system and FOPID controller is used to tune the system. The tuned parameters are minimized using a Particle Swarm Optimization (PSO) approach with Integral Time Absolute Error (ITAE) as the goal. When the suggested FOPID system's results are compared to those of PID-controlled systems, a sizable improvement is observed, which is explained by the results.

• Journal of Navigation and Port Research
• /
• v.29 no.3 s.99
• /
• pp.275-282
• /
• 2005

The year 2003 is the centennial of the birth of the modem lighthouse in Korea the lighthouse was originally surrounded by a beautiful nature and it contains the romantic sensitivity which relates with the ocean. And in some case it is a environment-friendly architectural facility which uses a alternative energy like a solar cell. Now the properly developed manned lighthouse is not only functioning as a traditional aids to navigation for the vessel, but also it becomes the new facility and space for all civilians who might visit and experience. If we want to vitalize the traditional lighthouse into water-familiar space, we must reconsider the facilities, various operational programs and the institutions for future-oriented development. For this situation we intended to reveal in this study that all the issues which relate to the proper use of the manned lighthouses in the whole country, since the project of water-familiar space started by MOMAF.

• Bulletin of the Korean Space Science Society
• /
• 2003.10a
• /
• pp.82-82
• /
• 2003

It is well known that electromagnetic (EM) waves are mode converted to electrostatic (ES) waves in inhomogeneous plasmas. We examine this issue in a three-dimensional multi-fluid numerical model. First, we derive a set of coupled linear wave equations when a one-dimensional inhomogeneous density profile is assumed in a cold and collisionless plasma. The massive ions are considered as fixed because we are interested in high frequency waves in plasmas. It is shown that the EM mode satisfies the 0th order modified Bessel equation near the resonant region where the frequency matches the local electron plasma frequency. It is expected that the EM waves are coupled and damped to the ES waves owing to the logarithmic singular behavior at such resonances. Second, we numerically test the same case in a 3-D multi-fluid model. An impulsive input is assumed to excite EM waves in the inhomogeneous 3-D box model. The wave spectra of electric and magnetic fields are presented and compared with the analytical results. Our results suggest that the EM energy is irreversibly converted into the ES energy wherever the resonant condition is satisfied. Finally we discuss how the mode conversion appears in both electric and magnetic fields by analyzing time histories of each component. We also compare our results with MHD wave coupling. It is numerically confirmed in this study that the coupling of EM and ES waves is similar to that of compressional and transverse MHD waves.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• v.29 no.1
• /
• pp.21-29
• /
• 2005

The year 2003 is the centennial of the birth of the modern lighthouse in Korea. The lighthouse was originally surrounded by a beautiful nature and it contains the romantic sensitivity which relates with the ocean. And in some case it is a environment-friendly architectural facility which uses a alternative energy like a solar cell. Now the properly developed manned lighthouse is not only functioning as a traditional aids to navigation for the vessel, but also it becomes the new facility and space for all civilians who might visit and experience. Jeju regional maritime affairs & fisheries office has developed the manned lighthouses properly to ocean cultural space for the past several years. As a result of that, the recognition regarded on ocean culture was raised and the regional tourism was vitalized. For this situation we intended to reveal in this study that all the issues which relate to the proper use of the manned lighthouse in the Jejudo, since the project of water-familiar space started by MOMAF.

• Journal of The Korean Astronomical Society
• /
• v.36 no.1
• /
• pp.21-31
• /
• 2003

ASTRO-F /FIS will carry out all sky survey in the wavelength from 50 to 200 ${\mu}m$. At far infrared, stars and galaxies may not be good calibration sources because the IR fluxes could be sensitive to the dust shell of stars and star formation activities of galaxies. On the other hand, asteroids could be good calibration sources at far infrared because of rather simple spectral energy distribution. Recent progresses in thermal models for asteroids enable us to calculate the far infrared flux fairly accurately. We have derived the Bond albedos and diameters for 559 asteroids based on the IRAS and ground based optical data. Using these thermal parameters and standard thermal model, we have calculated the spectral energy distributions of asteroids from 10 to 200 ${\mu}m$. We have found that more than $70\%$ of our sample asteroids have flux errors less than $10\%$ within the context of the best fitting thermal models. In order to assess flux uncertainties due to model parameters, we have computed SEDs by varing external parameters such as emissivity, beaming parameter and phase integral. We have found that about 100 asteroids can be modeled to be better than $5.8\%$ of flux uncertainties. The systematic effects due to uncertainties in phase integral are not so important.

• The Journal of Korea Robotics Society
• /
• v.8 no.4
• /
• pp.247-255
• /
• 2013

This paper shows the development of a snake robot (KAEROT-snake V) which consists of 16 1-DOF actuator modules and head module. The modules are connected serially and the joint axis of each module is rotated by $90^{\circ}$ with respect to the previous joint so that the snake robot can move in the 3D space. A tail actuator module includes slip-ring and metal connector. KAEROT-snake IV developed in prior research could move in the 3D space and climb up in a narrow pipe. But its design was not appropriate to the unstructured tough environment and its speed was somewhat slow. A new actuator module is designed to enclose all parts of the module so that any wire is not exposed. The size and weight of the new module was slightly reduced. And the rotation speed and torque of the joint was increased by about twice when compared with pre-module. An embedded controller was developed so small that it can be mounted inside the module. The performance of the developed robot was demonstrated through various locomotion experiments.

• Journal of the Korean Solar Energy Society
• /
• v.35 no.5
• /
• pp.1-10
• /
• 2015

Whereas recent domestic buildings and industrial facilities are being constructed as large as possible, the daylighting systems for the large space have rarely been developed. Domestic situation has been reported as only several small or medium sized daylighting systems have been developed, and the large scaled systems have entirely being imported from abroad. We have developed a large scaled daylighting system for the big space. The developed system have been evaluated in terms of the average system efficiency and daylighting factor. Each results are shown with tabulated experimental data.