• 한국재료학회지
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• 제24권7호
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• pp.339-343
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• 2014

$CaWO_4:Sm_x$(x = 0, 0.5, 1.0, 1.5, 2.0 mol%) white phosphors with different concentrations of $Sm^{3+}$ ions were synthesized using the hydrothermal method. The crystal structure, surface, and optical properties of the $CaWO_4:Sm_x$ phosphors were investigated using X-ray diffraction(XRD), field-emission scanning electron microscopy(FE-SEM), photoluminescence(PL) and photoluminescence excitation(PLE). From the XRD results, the crystal structure of the $CaWO_4:Sm$ phosphors was found to be tetragonal. The $CaWO_4:Sm$ phosphors became more cohesive with increasing $Sm^{3+}$-ion concentration. The photoluminescence excitation(PLE) peak of the phosphors, at around 250 nm, was ascribed to the transition from the 1A1 ground-state to the high-vibration level of 1T2 in the $WO{_4}^{2-}$ complex. The maximum emission spectra of the phosphors were observed when the $Sm^{3+}$ concentration was 0.5 mol%. The luminescence intensity of the $CaWO_4$ phosphors was decreased for $Sm^{3+}$ concentrations greater than 0.5 mol%.

• 소음진동
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• 제7권1호
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• pp.43-53
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• 1997

This paper investigated the practical use for measuring the structural intensity (power flow per width of cross section) in a uniform semi-infinite beam in flexural vibration. The structural intensity is obtained as a vector at a measurement point, One-dimensional structural intensity can be obtained from 4-point cross spectral measurement, or 2-point measurement on the assumption of far field. The measurement errors due to finite difference approximation and phase mismatch of accelerometers are examined. For precise measurements, it would be better to make the value of k$\delta$(wave number x space between accelerometers) between 0.5 and 1.0. Formulation of the relation between bending waves in structures and structural intensity makes it possible to separate the wave components by which one can get a state of the vibration field. Experimental results are obtained from 2- and 4-point measurement performed at 200mm (near field) and 400mm (far field) apart from excitation point in random excitation. the results are compared with the theoretical values and measured values of input power spectrum in order to verify the accuracy of structural intensity method, 2-point method is suggested as the practical structural intensity method.

• Biomolecules & Therapeutics
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• 제10권1호
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• pp.1-6
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• 2002

The particle size of medicinal materials is an Important physical property that affects the phar-maceutical behaviors such as dissolution, chemical stability, and bioavailability of solid dosage forms. The size reduction of raw medicinal powder is needed to formulate insoluble drugs or slightly soluble medicines and to improve the pharmaceutical properties such as the solubility, the pharmaceutical mixing, and the dispersion. The objective of the present study is to evaluate physiological activity of amorphous and nano-particle prep-arations of insoluble drug, ursodeoxycholic acid (UDCA), which were made by three types of fine grinding mills. The change of physical properties of ground UDCA was conformed by Mastersiger microplus and X-ray diffraction. We have investigated hepatoprotective effects of the nano-particle preparations of UDCA by plan-etary mill, vibration rod mill and jet mill in $CCI_4$-induced oxidatively injured mouse liver. The results showed that nano-particle preparations of UDCA all decreased reactive oxygen sepecies generation and lipid peroxi-dation in $CCI_4$-induced oxidative stress mice. Among them, nano-particle preparations by vibration rod mill and jet mill showed more significantly hepatoprotective effects compared to intact UDCA and planetary mill-ground UDCA. These results suggest that ground UDCA with vibration rod mill and jet mill shows a high amorphous state and the improved dissolution.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.672-675
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• 2006

It is becoming more significant to develop a rotary VCM type actuator for small form factor ODD, as portables are getting more and more popularized nowadays. In this paper, the procedure of development of the actuator which is applicable to compact flash II card and is fit in the specification of BD 1X is explained. This is based on the rotary VCM type actuator, which is good for reducing thickness. Air core solenoid coil is used in order to do focusing mechanism. And the total weight is reduced by using the structure of steel-aluminium-steel triple layer, so, the stiffness is still adequate. Additionally, the tracking coil is moved next to the actuator, so the total length was reduced, then the actuator become applicable to compact flash II card. The force of Magnetic Circuit is improved by using Magnetic Circuit DOE. And flexible mode frequency improved through the DOE of structure part. Modeling was exactly done in consideration of air core solenoid coil and pivot bearing. It is confirmed that the designed model is satisfied with the specification of BD 1X and is applicable to Compact Flash II card.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.393-398
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• 2004

The near-field scanning micro scope (NSOM) technique is in the spotlight as the next generation storage device. Many different types of read/write mechanism for NSOM have been introduced in the literature. In order for a near-field probe to be successfully implemented in the system, a suitable slider and suspension are needed to be properly designed. The optical slider is designed considering near-filed optics and probe array. The suspension generally supports slider performance, and tracking servo capacity in HDD. Moreover, the suspension for optical slider also should meet the optical characteristics, and is also required to satisfy shock performances for the mobility for the actuator. In this study, the optical slider and the suspension fer near-field probe array are designed and analyzed.

• 한국전기전자재료학회논문지
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• 제14권9호
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• pp.726-730
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• 2001

Temperature stabilities of dielectric constraints and resonant frequencies of the substrates are very important in piezoelectric ceramics oscillators and filters. In this study, it was investigated temperature stability of the length-extensional vibration mode of Pb(Zr$\_$y/Ti$\_$1-y/)O$_3$+x[wt%]Cr$_2$O$_3$ ceramics. The mode can be utilized in fabricating ultra-small 455 kHz IF devices. Addition of Cr$_2$O$_3$ in morphotrophic phase PZT decreased the variations of dielectric constant, electro-mechanical coupling factor k$\_$31/ and resonant frequency by thermal shock. As additive weight of Cr$_2$O$_3$increased, the temperature coefficient of resonant frequency changed from positive number to negative one. And the composition tith temperature coefficient of resonant frequency was shifted to the one with increased Cr$_2$O$_3$ additive weigh by thermal aging.

• 대한물리의학회지
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• 제13권1호
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• pp.63-72
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• 2018

PURPOSE: The aim of this study was to compare the effect of whole body vibration stimulation on ankle instability, ankle range of motion, and balance ability in adult with chronic ankle instability. METHODS: Forty-five adult with chronic ankle instability were randomly equally allocated the I group (whole body vibration stimulated at 10 Hz), or the II group (20 Hz), or the III group (25 Hz). All the participants (male:13/female: 32, age: $26.64{\pm}3.14$) in this study received whole body vibration therapy for an additional 15 minutes after hot pack and ultrasound three times a week for four weeks. Outcome were measured before and after 4 weeks training. RESULTS: All the three groups showed significant differences in AII and CAIT after intervention (p<.05). I group showed the most significant difference (p<.05). All the three groups also showed significant increase in ankle dorsiflexion and plantar flexion after training (p<.05). I group showed greater increase than the other groups in ankle dorsiflexion (p<.05). The X-axis, Y-axis, and fluctuation speed were significantly decreased in the three groups (p<.05), but there was no significant difference between the three groups after the intervention. CONCLUSION: The findings suggest that the whole body vibration stimulation according to various frequencies is effective for improve ankle instability, ankle range of motion and balance ability in adult with chronic ankle instability. 10 Hz whole body vibration stimulation could help improve ankle instability and ankle range more effectively than other frequencies.

• Journal of Biosystems Engineering
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• 제40권1호
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• pp.28-34
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• 2015

Purpose: This study aimed to install an RTK-GPS (Real Time Kinematic-Global Positioning System) and IMU (Inertial Measurement Unit) on a tractor used in a farm to measure positions, pasture topography, posture angles, and vibration accelerations, translate the information into maps using the GIS, analyze the characteristics of grass harvesting work, and establish new technologies and construction standards for pasture infrastructure improvement based on the analyzed data. Method: Tractor's roll, pitch, and yaw angles and vibration accelerations along the three axes during grass harvesting were measured and a GIS map prepared from the data. A VRS/RTK-GPS (MS750, Trimble, USA) tractor position measuring system and an IMU (JCS-7401A, JAE, JAPAN) tractor vibration acceleration measuring systems were mounted on top of a tractor and below the operator's seat to obtain acceleration in the direction of progression, transverse acceleration, and vertical acceleration at 10Hz. In addition, information on regions with bad workability was obtained from an operator performing grass harvesting and compared with information on changes in tractor posture angles and vibration acceleration. Results: Roll and pitch angles based on the y-axis, the direction of forward movements of tractor coordinate systems, changed by at least $9-13^{\circ}$ and $8-11^{\circ}$ respectively, leading to changes in working postures in the central and northern parts of the pasture that were designated as regions with bad workability during grass harvesting. These changes were larger than those in other regions. The synthesized vectors of the vibration accelerations along the y-axis, the x-axis (transverse direction), and the z-axis (vertical direction) were higher in the central and northwestern parts of the pasture at 3.0-4.5 m/s2 compared with other regions. Conclusions: The GIS map developed using information on posture angles and vibration accelerations by position in the pasture is considered sufficiently utilizable as data for selection of construction locations for pasture infrastructure improvement.

• Journal of Biosystems Engineering
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• 제29권2호
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• pp.101-108
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• 2004

The objectives of this study were to determine the natural frequency of a walking-type cultivator's handle using a modal analysis, to determine whether or not the handle resonates with forcing frequency induced by its engine, and to determine a method to reduce the handle vibration using a technique of the operational deflection shapes(ODS). Results of the study are as follows: The natural frequencies of the handle up to third harmonics were found to be 20.4, 22.5 and 92.1 Hz in the vertical direction and 14.9, 93, and 132 Hz in the horizontal direction. It was found that the handle does not resonate with the forcing frequency of the engine, which is 52 Hz. The operational deflection shape analysis revealed the deflected shapes of the handle in the vertical and horizontal directions and suggested that the handle vibration can be reduced by adding some mass to the place where the largest deflection occurs. Attaching of 1.1 kg mass adjacent to the largely deflected area resulted in reductions of vibration from 9.45 to 8.03 m/s$^2$ in x-axis direction from 3.89 to 3.16 m/s$^2$ in y-axis direction and from 7.89 to 3.09 m/s$^2$ in z-axis direction, which are respectively 15, 19 and 61% reductions. The total vibration level was reduced by 29%, indicating that mass-adding method by the ODS is very effective for reducing the handle vibrations of the cultivators.

• Journal of Ginseng Research
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• 제8권2호
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• pp.105-113
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• 1984

This study was conducted to investigate chemical and physical characteristics of pectin in Korean ginseng plant. The results obtained are as follows: 1, The molecular weight of the pectin in ginseng plant was in the range of 1.1-2.4x 104 and athydrouronic acid content in the pectin was 97.98%. 2. The intrinsic viscosity of pectin as well as apparent visosity of the pectin in the roots were increased with cultural period. 3. The IR spectra of ginseng pectin showed the OH stretch, C-H bending vibration and the vibration of ester group carboxyl. 4. Sugars present in galacturonic acid, glucose, arbinose, xylose, galactose and rhamnose.