• The Journal of Society for e-Business Studies
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• v.23 no.2
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• pp.111-121
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• 2018

Many problems in rotating machinery such as aircraft engines, wind turbines and motors are caused by bearing defects. The abnormalities of the bearing can be detected by analyzing signal data such as vibration or noise, proper pre-processing through a few signal processing techniques is required to analyze their frequencies. In this paper, we introduce the condition monitoring method for diagnosing the failure of the rotating machines by analyzing the vibration signal of the bearing. From the collected signal data, the normal states are trained, and then normal or abnormal state data are classified based on the trained normal state. For preprocessing, a Hamming window is applied to eliminate leakage generated in this process, and the cepstrum analysis is performed to obtain the original signal of the signal data, called the formant. From the vibration data of the IMS bearing dataset, we have extracted 6 statistic indicators using the cepstral coefficients and showed that the application of the Mahalanobis distance classifier can monitor the bearing status and detect the failure in advance.

• Journal of the Korean Institute of Intelligent Systems
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• v.21 no.1
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• pp.80-85
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• 2011

This paper presents the design of the power-assisted controller for the in-wheel type smart wheelchair by using torque estimation that is predicted by relationship between input voltage and output wheel angular velocity. Nowadays, interest of the moving assistant aids is increased according to the increase in population of the elderly and the handicapped person. However some of the moving assistant aids have problems. For example, manual wheelchair has difficulty moving at the slope, because users lack the muscular strength of their arm. In electric wheelchair case, users should be weak by being decreased muscles of upper body. To overcome these problems, power-assisted electric wheelchair are proposed. Most of the power-assisted electric wheelchair have the special rims that can measure the user's power. In here, the rims have to be designed to install the sensors to measure user's power. In this paper, we don't design the rim to measure the man power. To predict the man power, we propose a control algorithm of the in-wheeled electric wheelchair by using torque estimation from the wheel. First, we measure the wheel velocity and voltage at the in-wheel electric wheelchair. And then we extract driving will forces by using proposed mathematical model. Also they are applied at the controller as the control input, we verify to be able to control in-wheel type smart wheelchair by using simulation.

• Journal of the Korean Institute of Gas
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• v.20 no.6
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• pp.43-49
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• 2016

In this paper, purpose of study is emissions characteristics according to effects of heating value variations of CNG fuel in a dual-fuel engine fueled by diesel and natural gas. For heating value variation of CNG fuel, nitrogen gas was mixed with pure CNG fuel. So the higher heating value was changed from $10,400kcal/Nm^3$ to $9,400kcal/Nm^3$. Under one condition of CNG substitution rate was fixed at 80%, diesel fuel was injected at a fixed injection timing of 16 CAD BTDC and fuel pressure was also fixed at 110 MPa. The condition of tested engine was 1800 rpm and 500Nm. Emissions were sampled in exhaust pipe was located at downstream turbocharger. As a result, emissions characteristics were checked in heating value variations of CNG fuel with mixed nitrogen gas THC, $CH_4$ and CO emissions decreased and NOx and $CO_2$ increased.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.8
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• pp.1795-1801
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• 2009

In this study, a portable flashlight which can manually generate the electricity by using sunlight was developed so that it can be used in the extreme environmental condition such as no-electricity condition. Battery is charged by using solar battery during the day, but when sunlight is not avalible during the night or rainy day, a handle is rotated to generate the electricity in order to charge the battery manually. To improve the brightness of the light, light is concentrated by using the optical lens. Low electric consumption circuit is used for the longer operating time by suppress electrical consumption while lamp is discharged. A circuit is designed and used for steady electrical curris dand voltage to insure steady battery charging. Super-discharge circuit and protection circuit are used for the super discharge of battery when it is not used for a long time. Also the constant charge is possible by using houseware adapter. As a result, a portable flashlight is designed to charge with sunlight during day, and with houseware adapter during night. A portable flashlight is also designed to irradiate longer distances by improvement of the brightness of the light using the optical lens. Thus, it forms white natural ray of light making possible for night reading.

• Korean Journal of Mineralogy and Petrology
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• v.35 no.3
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• pp.259-271
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• 2022

Lattice preferred orientation (LPO), which shows a specific lattice-orientation of minerals, is affected by the deformation conditions of minerals. Because of this reason, LPO is very useful to study the deformation conditions of the minerals and the rocks. In this study, we collected amphibole-rich rocks from the Geumgye Mountain, Chugye-ri, Yugu-eup, Chungcheongnamdo, located in the southwestern part of the Gyeonggi Massif, and analyzed the LPO of amphibole and plagioclase using electron backscattered diffraction. Two types of LPOs of amphibole, type I and type IV, were observed in Yugu amphibole-rich rocks. Our data suggest that the amphibole-rich rocks in Yugu were deformed by rigid body rotation regardless of the LPOs and grain size of amphibole, and the LPOs are considered to have been affected by the degree of deformation (i.e. strain). In the low strained amphibole-rich rock, a strong type I LPO and a large grain size of amphibole were observed. On the other hand, in the highly strained amphibole-rich rocks, a weak type IV LPO and a small grain size of amphibole were observed. The various degree of deformation observed in the Yugu amphibole-rich rocks were also observed in the adjacent peridotites, indicating that the rocks in Yugu experienced various levels of deformation.

• Economic and Environmental Geology
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• v.54 no.2
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• pp.233-245
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• 2021

Many studies on the microstructures in rocks have been conducted using experimental methods with various equipment as well as natural rock studies to see the development of microstructures and understand their mechanisms. Grain boundary migration of mineral aggregates in rocks could cause grain growth or grain size changes during metamorphism or deformation as one of the main recrystallization mechanisms. This study suggests improved ways regarding the analog material experiments with reformed equipment to see sequential observations of these grain boundary migration. It can be more efficient than the existing techniques and carry out an appropriate microstructure analysis. This reformed equipment was implemented to enable optical manipulation by mounting polarizing plates capable of rotating operation on a stereoscopic microscope and a deformation rig capable of experimenting with analog materials. The equipment can automatically control the temperature and strain rate of the deformation rig by microcontrollers and programming and can take digital photomicrographs with constant time intervals during the experiment to observe any microstructure changes. The composite images synthesized using images by rotated polarizing plates enable us to see more accurate grain boundaries. As a rock analog material, norcamphor(C7H10O) was used, which has similar birefringence to quartz. Static grain growth and simple shear deformation experiments were performed using the norcamphor to verify the effectiveness of the equipment. The static grain growth experiments showed the characteristics of typical grain growth behavior. The number of grains decreases and the average grain size increases over time. These case experiments also showed a clear difference between the growth curves with three temperature conditions. The result of the simple shear deformation experiment under the medium temperature-low strain rate showed no significant change in the average grain size but presented the increased elongation of grain shapes in the direction of about 53° regarding the direction perpendicular to the shearing direction as the shear strain increases over time. These microstructures are interpreted as both the plastic deformation and the internal recovery process in grains are balanced by the deformation under the given experimental conditions. These experiments using the reformed equipment represent the ability to sequentially observe changing the microstructure during experiments as desired in the tests with the analog material during the entire process.

• Korean Journal of Food Science and Technology
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• v.45 no.4
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• pp.428-433
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• 2013

Heterogenous samples of locust bean gum (galactomannan) were prepared into homogeneous substances. Locust bean gum was fractioned using ammonium sulfate (14.11-23.08%, w/w). The intrinsic viscosity was obtained by extrapolating reduced viscosity versus concentration by using an Ubbelohde viscometer. The ranges of intrinsic viscosity for fractions that not included protein (F3-F6) and fractions that included protein (F1-F2) were 9.89-8.10 and 8.44-4.59, respectively. Values for Huggins' coefficient (k'), which depends on physical interactions, were 0.46-0.78. Increasing ammonium sulfate concentration was associated with a weak trend towards lower molecular weight and intrinsic viscosity by size-exclusion chromatography (SEC): $M_w$ ranged from 674 to 617 kg/mol and [${\eta}$] from 9.80 to 8.10 dL/g between F3 and F6. The evaluations of those fractions by using SEC and the Ubbelohde viscometer produced very similar values, as predicted. We verified the application of a gradient of ammonium sulfate to precipitate locust bean gum into fractions of different molecular size and show structural variations.