• Journal of Korea Multimedia Society
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• v.19 no.2
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• pp.128-137
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• 2016

In mobile communication, air conduction(AC) speech signal had been commonly used, but it was easily affected by ambient noise environment such as emergency, military action and rescue. To overcome the weakness of the AC speech signal, bone conduction(BC) speech signal have been used. The BC speech signal is transmitted through bone vibration, so it is affected less by the background noise. In this paper, we proposed noise cancellation algorithm of the BC speech signal using noise feature of decomposed bands. The proposed algorithm consist of three steps. First, the BC speech signal is divided into 17 bands using perceptual wavelet packet decomposition. Second, threshold is calculated by noise feature during short time of separated-band and compared to absolute average of the signal frame. Therefore, the speech and noise parts are detected. Last, the detected noise parts are removed and then, noise eliminated bands are re-synthesised. In order to confirm the efficiency of the proposed algorithm, we compared the proposed algorithm with conventional algorithm. And the proposed algorithm has better performance than the conventional algorithm.

• Journal of the Korean GEO-environmental Society
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• v.14 no.8
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• pp.45-51
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• 2013

In the construction site of underground buildings which have severe environment such as dust, noise, vibration, the technology of rescue the builders in the construction site when accident occurs by tracking the location of the builders and express the mission of supervisor smoothly. In this study, in order to acquire the location information of the builders in the construction site of underground buildings by using MEMS INS and air pressure sensor, we firstly performed the field test in construction site, analyzed the location and the elevation accuracy based on the detected results, and then verified its practicality and rationality after all. As a result, we could acquire worker's position-accuracy within 10m in horizontal direction and 4m in vertical direction. Therefore we could judge availability in construction fields of underground structure.

• Journal of Practical Engineering Education
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• v.5 no.2
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• pp.169-176
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• 2013

Recently the construction of simulation environment is an important issue in all fields. In case of the training for operating machines such as airplanes or spaceships which cause a huge cost, simulators could be helpful to reduce the costs and training efforts by simulating real situations. When people get a driver's license, too many trainees have to wait for their turns because of the limited number of cars and the small space of training sites. To solve this problem, we have designed and developed the basic design for the simulators. We suggest the Computer 3D Simulation Model for a driver's practice. The concept of this simulator is from a 3D Racing-game which suits for a driving exercise. We provide users with handle-controlled simulation settings to let users feel reality as if they drive in real through this simulator. We also use a 'force-feedback' system which gives handle vibration when users collide against obstacles or exceed lanes. Users can be absorbed in the simulation program and feel the sense of the real. This paper is the study about modeling the driving exercise model of 'computer 3D simulation', and producing and utilizing the simulator through this modeling.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.1
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• pp.102-108
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• 2016

A flying drone generates vibrations in a great variety of frequencies, and it requires a gimbal system stabilization loop design in order to obtain clean and accurate image from the camera attached to the drone under this environment. The gimbal system for drone comprises the structure that supports the camera module and the stabilization loop which follows the precise angle while blocking the vibration from outside. This study developed a dynamic model for one axis for the stabilization loop design of a gimbal system for drones and applied classical PID controller and intelligent PID controller. The Stabilization loop design was developed by using MATLAB/Simulink and compared the performance of each controller through simulation. Especially, the intelligent PID controller can be designed almost without the dynamic model and it demonstrates that the angle can be followed without readjusting the parameters of the controller even when the characteristics of the model changes.

• Journal of Environmental Impact Assessment
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• v.23 no.6
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• pp.517-526
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• 2014

This paper performed studies on a guide for an environmental assessment necessary to select railroad route optimally, and presented techniques for an environmental friendly route selection using AHP(Analytical Hierarchy Process) as an objective method. The AHP is an approach to decision making that involves multiple choice criteria into a hierarchy and assessing the relative importance of each criterion, and determining an overall ranking of the alternatives. For the purpose of this study, we established the weight and the order of major environmental assessment items based on the survey of experts. The results of the weight by AHP were in order of Fauna & Flora, Topography & Geology, Nature Environmental Assets, Noise & Vibration, Water Quality, Landscape and Air Quality indicating natural environment should be in priority. To develop the more efficient environmental friendly route selection systems, it is necessary to consider economical, technical, and social aspects in addition to environmental consideration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.840-843
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• 2002

The dry pulverizing/Mixing device is used to deal with the spent fuels for the safe disposal. The separated pellets from hulls by a slitting device are put and oxidized from UO$_2$ solid pellet to U$_3$O$\_$8/ powder in the device. The device have been developed based on a voloxidation method which is one of several dry de-cladding methods. We have benchmarked dry de-cladding methods, analyzed applicability to the advanced spent fuel management process, integrated and compared several configuration, and finally derived detailed specifications proper to requirements for the device. Also, thermal characteristics of the device such as thermal stress and strain have been analyzed by the commercial software, 1-DEAS, and the reliability of the results have been verified by the KOLAS(Korea Laboratory Accreditation Scheme). The UO$_2$ solid pellets are put in the device which has a capacity of 20 kgHM per a batch, heated up about 600$^{\circ}C$ in the air environment. Then, the UO$_2$ solid pellets are oxidized into the U$_3$O$\_$8/ powder, and the powder is collected in a special vessel. The device has been designed and developed as fellows: the multi-staged fine hole meshes are used to reduce the size of the powder gradually, heat and air(oxygen) are supplied continuously to reduce the reaction time, and slight vibration effect are applied to collect powder cling to the device.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.8
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• pp.605-612
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• 2013

When developing medium satellites or large satellites, coupled load analysis(CLA) is performed in order to verify satellite design as a final assessment under launch environment. Maximum acceleration, gap between adjacent parts, internal loads obtained from CLA are used to assess the safety of satellite design by comparing them with the allowable loads of every component. To achieve reliable CLA results, satellite FE model have to be properly updated to match with the sine vibration test results. In this paper, the validation procedure of satellite FE model and its results are discussed.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.622-622
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• 2013

Piezoelectric energy harvesting (PEH) device refers to a power device for acquiring mechanical energy from the environment surrounding us which would otherwise be wasted and for converting it into usable electrical energy. While much work has been done on developing ZnO nanogenerator (NG) with nanowire arrays, there are some issues of not only scaling up its output power but also optimizing structure for operating feasibly in various conditions. Efficiency of NG is highly dependent on fixed orientation. But in many cases, it is not easy to predict where the pressure and vibration may come from. Furthermore, the direction of the applied mechanical stress is usually non-stationary and can be random in various practical applications. Therefore an omnidirectional PEH is needed.In this work, we investigate an omnidirectional PEH device consisting ZnO nanowires. We deposited spiral patterned ZnO seed layer on Kapton film. We deposited thin Cr layer on the ZnO seed layer using DC-sputter to form a passivation layer to retard un-expected growth of ZnO nanowires. We grew ZnO nanowires along the spiral arms using hydrothermal method. ZnO nanowires have been selectively grown from the ZnO sidewall without Cr layer and have the average length of$5{\mu}m$ and the average diameter of 40nm. We reduced the defect in the as-grown ZnO nanowires by O2 plasma using asher and by thermal treatment using RTA. Consequently, each nanowire has different directions to each other. This isotropic design can lead to the omnidirectional power generation. The morphology of NG is characterized with FESEM. Maximum output power of the device is measured by using a picoammeter and a nanovoltmeter.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.101-110
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• 2004

Flight and Qualification Models of Single Board Computer (SBC), called On-Board Computer (OBC), for HAUSAT-l picosatellite, which is scheduled to launch on September, 2004 by Russian "Dnepr" launch vehicle, have been developed. The OBC of HAUSAT-1 has been designed with some improved features compared to other picosatellites. A multifunctional controller and up-to-date SPI (Serial Peripheral Interface) and 1-Wire interface are implemented to simplify the harness routing and to minimize the mass and size of OBC. The improved fault-tolerant architecture design methodology is incorporated in the HAUSAT-1 OBC to protect against space radiation environment. The functions of the OBC were fully tested and verified by the Electrical Test Bed (ETB) model. This paper is also addressing the environmental test results, such as random vibration and thermal vacuum tests.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.4
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• pp.345-356
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• 2004

Open-cut method has been widely used to construct underground structures, but it causes several problems such as traffic congestion and public resentment resulting from severe construction noise and ground settlement. In many cases, it is very difficult to build underground structures safely due to the unknown locations of buried facilities such as water pipes, drainage pipes, gas pipes and high-pressure cable conduits etc. Also in open-cut method, moving buried facilities causes additional cost and extension of construction period. Therefore, this paper is to present a case study in which Tubular Roof construction Method (T.R.c.M.), a newly developed construction method for underground structures using slab steel pipes and PC wall trench, is applied for the construction of a subway tunnel in Seoul. As a result, it is found that T.R.c.M. is a construction method by which tunnels can be constructed safely without any effect on the surrounding environment and traffic flow due to the minimized construction vibration and noise.