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In this paper, a cross-shaped piezoelectric generator was proposed for generating electric power at low frequency range. The generator has centrosymmetric four elastic body legs which have equivalent vibration mode. The centrosymmetric structure of the generator is able to generate in each elastic body legs at the same time using only one vibration source. Vibration is transferred from center of the generator and is equally applied to each elastic body leg. So each elastic body leg of the generator has the same resonance frequency and vibration mode. Resonance and output characteristics of the generator were analyzed by FEM program. Output characteristics of the generator could be changed by elastic body length, elastic body thickness, ceramic width, ceramic thickness and additional mass at the edge of elastic body legs. Based on FEM result, a generator was fabricated and experimented. As a result, resonance frequency of the generator was verified lower than 35 Hz. So we confirmed generating possibility of the generator at low frequency range.

Structure of the octagon-type ultrasonic motor was proposed and designed so as to allow the motor to drive small actuator. The stator of the motor consisted of the octagon shape elastic body and four rectangular plate ceramics. The four ceramics were attached to outer surfaces of the octagon elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90° phase difference voltages were applied to the ceramics on vertical surfaces. When the AC voltage with 90° phase difference was applied in ceramics, the elliptical displacement of unimorph bars was generated by generating bending vibration. To find the maximum displacement model that generates elliptical displacement at the centers of the inner surfaces, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As a result, the speed and torque are increased linearly by increasing the input voltage and the speed of motors can be controlled by changing the applied voltages.

A cantilever-type piezoelectric generator has advantages of simple structure, ease of fabrication and large displacement by transverse vibration of a beam. It is easy to control the natural frequency, and also possible to increase the output power by changing the length, width, and thickness of the generator. In particular, the length increases, the natural frequency sharply decreases, and vice versa. Hence, the natural frequency can widely be controlled by using change in the length of elastic body. In this paper, the generator was designed and fabricated to change natural frequency using the slides of the case. In addition, the generating characteristics were confirmed through finite element analyses and vibration experiment. As a result, the maximum output characteristics could be generated due to resonance phenomenon although any frequency of external force was applied.

A novel design of a simple square-frame USM (ultrasonic motor) was proposed. The stator of the motor consists of a square-frame shape elastic body and four rectangular plate ceramics. The four ceramics were attached to inner surfaces of the square frame elastic body. The same phase voltages were applied to the ceramics on horizontal surfaces, and 90 degree phase difference voltage were applied to the ceramics on vertical surfaces. To find a model that generates elliptical motion at outside of the stator, the finite element analysis program ATILA was used. The analyzed results were compared to the experimental results. As result, the model EL10EH3ET0.5CL4 which generates the maximum elliptical displacement was chosen by analyzing the resonance mode according to changes in frequency.

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Polymer Science and Technology, Chonbuk National University, Chonju, Chonbuk 561-756, KoreaDepartment of Chemistry, Kunsan National University, Kunsan, Chonbuk 573-701, KoreaReceived November 27, 2001Keywords : Raman, Liquid crystal, Intermolecular interaction, Coil effect, Hydrogen bonding.IntroductionLiquid crystalline polymers (LCPs) have been intensivelystudied for their scientific and technological interests. AmongLCPs, rod-coil types have recently drawn attention, parti-cularly in relation to their likelihood to form various kinds ofsupramolecules depending on chain lengths. The LCPs basedon a biphenyl ester moiety can have different microscopicstructures. Most poly(ethylene oxide)s (PEO)-based LCPsresult in a layered smectic mesophase

Purpose: To compare central macular thickness (CMT) and visual acuity outcomes after intravitreal injection of triamcinolone acetonide or bevacizumab for the treatment of diabetic macular edema (DME). Methods: Fifty-one patients were randomly choosen to receive an intravitreal injection of either triamcinolone acetonide or bevacizumab. Patients were retrospectively reviewed, and 28 of 51 received an intravitreal injection of triamcinolone acetonide while the remaining 23 received bevacizumab injection. All patients underwent Snellen visual acuity testing, optical coherence tomography imaging and ophthalmoscopic examination at baseline and at four weeks following the injection. Results: In the triamcinolone group, CMT decreased from 656.71 at baseline to 312.46 at the four-week follow-up visit, while in the bevacizumab group, CMT decreased from 582.17 at baseline to 453.09 at the follow-up (p0.38 to 0.670.33) compared to the bevacizumab group (from 0.790.31 to 0.700.34) [p

Purpose: To improve our understanding of the pharmacokinetics of triamcinolone acetonide (TA) and TA concentration in ocular tissue, TA concentration was measured in ocular tissue after intravitreal and subtenon injection. Methods: Fifteen rabbit eyes underwent subtenon TA injection (40 mg/1 ml), and another 15 rabbit eyes underwent intravitreal TA (4 mg/0.1 ml) injection. All eyes were enucleated at 1, 2, 4, 8, and 12 weeks after subtenon and intravitreal injection, and TA concentration in the aqueous and vitreous humor and the retina-choroid were measured by high performance liquid chromatography (HPLC). Results: In cases of subtenon's TA injection, TA concentrations were 0 ng/ml, 136.7 ng/ml, 178.7 ng/ml, 0 ng/ml, and 0 ng/ml in the aqueous humor; 99.1 ng/ml, 125.7 ng/ml, 726.8 ng/ml, 0 ng/ml, and 0 ng/ml in the vitreous humor; 72.7 ng/ml, 304.6 ng/ml, 459.0 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid after 1, 2, 4, 8, and 12 weeks, respectively. In cases of intravitreal TA injection, the measured values were 0 ng/ml, 0 ng/ml, 0 ng/ml, 654.1 ng/ml, and 0 ng/ml in the aqueous humor; 28152.2 ng/ml, 13646.4 ng/ml, 11388.8 ng/ml, 10297.2 ng/ml, and 183.0 ng/ml in the vitreous humor; and 0 ng/ml, 27.9 ng/ml, 108.3 ng/ml, 0 ng/ml, and 0 ng/ml in the retina-choroid at each time point. Conclusions: Intravitreal TA injection may be more effective for drug delivery than subtenon TA injection, but subtenon TA injection seems to be an effective and safe technique.