This study investigated the noise reduction effect according to the structure of the sound-absorption and insulating materials in order to maximize the noise reduction effect in various noise environments. For this purpose, the transmission loss according to the change in hole size of the performated plate in sound-absorption and insulating board was predicted using an CAE model. The sound-absorption and insulating board was modeled and the computation of the transmission loss was performed after applying the physical properties and boundary conditions. The pure sounds of 32Hz to 4,000Hz were generated, and the analysis was performed by changing the diameter and pitch of the perforated plate. It was confirmed that the influence of the diameter and pitch of the perforated plate is closely related to the structure that make up the sound-absorption and insulating material. In order to effectively reduce the variously changing noises, it is believed that a method of improving transmission loss for each frequency band of interest is needed by changing the structure of the sound-absorption and insulating material so that the diameter and pitch of the perforated plate can be changed.

Road surfaces and tires have a great influence on road noise in automobiles. Therefore, this study attempted to investigate the effect of changes in road surface and tire tread on road noise. For six road surfaces, road noise was measured and analyzed while changing two types of tire treads. In all frequency bands, the sound pressure of the road surface with a relatively large roughness was higher than that of other roads. And in the case of a road surface with relatively large pore, it was investigated that noise was reduced compared to other road surfaces due to the sound absorption effect in the low frequency area. On roads with irregular road roughness, the high sound pressure was exhibited in all frequency bands regardless of tire tread, indicating an increase in road noise due to irregular wear on roads. It was confirmed that the noise deviation due to the change in road surface was larger than the noise deviation due to the tire structure, and it is judged that noise research according to the structure and condition of the road surface.

Speaker is the converting device which change electric energy to sound energy, and we can easily see the speaker. They are widely used to home and car audio unit, home and industrial alarm device. Sometimes, the alarm sounds cause the environmental noise. Therefore it is important to design the appropriate speaker according to the installed device and position. In order to study the vibration and sound characteristics, the curvature of the cone paper is changed. Finite element method is used to compute the vibration characteristics and mode. Indoor and Vehicle teats are carried out to investigate the non-linear characteristics and the sound characteristics for some car speakers.

Tungsten disulfide (WS2), a typical 2D layerd structure, has received much attention as a pseudocapacitive material because of its high theoretical specific capacity and excellent ion diffusion kinetics. However, WS2 has critical limits such as poor long-term cycling stability owing to its large volume expansion during cycling and low electrical conductivity. Therefore, to increase the high-rate performance and cycling stability for pseudocapacitors, well-dispersed WS2 nanoparticles embedded in carbon nanofibers (WS2-CNFs), including mesopores and S-doping, are prepared by hydrothermal synthesis and sulfurizaiton. These unique nanocomposite electrodes exhibit a high specific capacity (159.6 F g−1 at 10 mV s−1), excellent high-rate performance (81.3 F g−1 at 300 mV s−1), and long-term cycling stability (55.9% after 1,000 cycles at 100 mV s−1). The increased specific capacity is attributed to well-dispersed WS2 nanoparticles embedded in CNFs that the enlarge active area; the increased high-rate performance is contributed by reduced ion diffusion pathway due to mesoporous CNFs and improved electrical conductivity due to S-doped CNFs; the long-term cycling stability is attributed to the CNFs matrix including WS2 nanoparticles, which effectively prevent large volume expansion.

Most of speakers, the con-paper (con shape) or vibration plate generate the sound by reciprocating motion which is received vibrating signal from voice coil. On the other hand, the vibration speaker that reproduces sound by attaching a vibration head to some materials such as wood, plastic, glass plate, etc. instead of cone paper or vibration plate generates different sound timbres depending on the attached materials with vibration head. so we can hear a variety of timbres than ordinary speakers. In this study, the characteristics of vibration and sound propagation according to various materials attached to the vibration head of the vibration speaker were experimentally investigated and this sound propagation characteristics were compare with woofer speaker and micro speaker. As a result of sound propagation characteristics of vibration speaker, the reproduction ability of low frequency band wes inferior to compared than woofer speaker and micro speaker. This is judged to be due to the material characteristics of glass and wood which are source of the sound propagation. As compare with 1kHz sine tone, the woofer speaker has not generated the high order harmonic component, but the glass plate and wood plate used with the vibration speaker head have generated the high order harmonic component at a level that can not be ignored. According to above results, the vibration speaker will be had a low articulation of sound because the higher volume to generate the high distortion.

In the car speaker, because the sound characteristics is changed by the space of car which mount the speaker, the speaker elements must be decide according to sound field. In this study, the nonlinear characteristics, the frequency response and the sound pressure for the same size speakers which is adapted to domestic car model are investigated. The car model is classified to semi-midsize, midsized, full size automobile in order to change the car space. As a results, we can investigate the differences of the force factor and the stiffness of suspension system for speaker. According to the change of the speaker characteristics, the sound pressure is changed, also. In the future, these data will be used to investigate the correlation between the sound quality and measurement data.

This study investigates the noise characteristics of small DC motors and applies them to the production line of small DC motors to qualify. Because currently the noise and vibration are greatly reduced due to vibration reduction technology and sound insulation technology of engine and transmission development. For this reason, the noise and vibration problems of various small DC motors that have not been heard before are emerging. For this purpose, noise characteristics of good and bad products of company A and B which are most used at present are analyzed and noise characteristics are investigated.

In the present study, vanadium oxide(V2O5) films for electrochromic(EC) application are fabricated using sol-gel spin coating method. In order to optimize the EC performance of the V2O5 films, we adjust the amounts of polyvinylpyrrolidone(PVP) added to the solution at 0, 5, 10, and 15 wt%. Due to the effect of added PVP on the V2O5 films, the obtained films show increases of film thickness and crystallinity. Compared to other samples, optimum weight percent(10 wt%) of PVP led to superior EC performance with transmittance modulation(45.43 %), responding speeds(6.0 s at colored state and 6.2 s at bleached state), and coloration efficiency(29.8 cm2/C). This performance improvement can be mainly attributed to the enhanced electrical conductivity and electrochemical activity due to the increased crystallinity and thickness of the V2O5 films. Therefore, V2O5 films fabricated with optimized amount of PVP can be a promising EC material for high-performance EC devices.

The various hydraulic equipments including main control valves are composed of relatively long replacement parts, so the stability is very important. These systems ensure system safety by not delivering pressure to actuators when pressure exceeds the limiting pressure. According to various hydraulic equipments, the required pressure of every hydraulic actuators are differenced. So the optimal design of the main valve is indeed needed. In the previous study, the detail shapes and the boundary conditions of the main control valve were studied by CFD analysis using FLUENT. Based on the previous study, the optimal design of the main control valve is done by applying the parametric modeling technique and then the optimum design of the main control valve is investigated by CFD analysis.

Uniform TiO2 blocking layers (BLs) are fabricated using ultrasonic spray pyrolysis deposition (USPD) method. To improve the photovoltaic performance of dye-sensitized solar cells (DSSCs), the BL thickness is controlled by using USPD times of 0, 20, 60, and 100 min, creating TiO2 BLs of 0, 40, 70, and 100 nm, respectively, in average thickness on fluorine-doped tin oxide (FTO) glass. Compared to the other samples, the DSSC containing the uniform TiO2 BL of 70 nm in thickness shows a superior power conversion efficiency of 7.58±0.20% because of the suppression of electron recombination by the effect of the optimized thickness. The performance improvement is mainly attributed to the increased open-circuit voltage (0.77±0.02 V) achieved by the increased Fermi energy levels of the working electrodes and the improved short-circuit current density (15.67±0.43 mA/cm2) by efficient electron transfer pathways. Therefore, optimized TiO2 BLs fabricated by USPD may allow performance improvements in DSSCs.

Transparent conducting oxides (TCOs) were fabricated using solution-based ITO (Sn-doped In2O3) nanoinks with nanorods at an annealing temperature of 200 oC. In order to optimize their transparent conducting performance, ITO nanoinks were composed of ITO nanoparticles alone and the weight ratios of the nanorods to nanoparticles in the ITO nanoinks were adjusted to 0.1, 0.2, and 0.5. As a result, compared to the other TCOs, the ITO TCOs formed by the ITO nanoinks with weight ratio of 0.1 were found to exhibit outstanding transparent conducting performance in terms of sheet resistance (~102.3 Ω/square) and optical transmittance (~80.2%) at 550 nm; these excellent properties are due to the enhanced Hall mobility induced by the interconnection of the composite nanorods with the (440) planes of the short lattice distance in the TCOs, in which the presence of the nanorods can serve as a conducting pathway for electrons. Therefore, this resulting material can be proposed as a potential candidate for solution-based TCOs for use in optoelectronic devices requiring large-scale and low-cost processes.

The air conditioner is an instrument to make a low degree fresh wind by compress a refrigerant and through the heat exchanger. As change a refrigerant of low degree and low pressure to high degree and high pressure, it is needed to the compressor. The compressor compress a refrigerant by transfer the rotational energy to reciprocating energy. The goal of this research is for easy use to failure diagnosis of an automotive compressor according to vibration characteristics of each failure types of automotive compressor. To do this, we have prepared the normal products and made some detective products which several kinds of detective types to measure and analysis of vibration characteristics. From the results, we have made a close investigation into the vibration characteristics of each kinds of detective type.