• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.1
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• pp.27-36
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• 2001

In this paper, micromachined millimeter-wave cavity resonators ar presented. One-port and two-port cavity resonators at Ka-band are designed using 3D design software, HP $HFSS^{TM}$ ver. 5.5 Cavity resonators are fabricated on Si substrate, which is etched down for the cavity, bonded with a Quartz wafer in which metal patterns for the feeding line coupling slot are formed. One-port resonator shows the resonant frequency of 39.34 GHz, the return loss of 14.5 dB, and the loaded $Q(Q_{L})$ of 150. Two-port cavity resonator shows the resonant frequency of 39 GHz, the insertion and return losses of 4.6dB and 19,9dB, the loaded($Q_{L}$) and unloaded $Q(Q_{U})$) of 44.3 and 107, respectively.

• ETRI Journal
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• v.46 no.3
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• pp.404-412
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• 2024

We propose a method for increasing the bandwidth of a substrate-integrated-waveguide (SIW) cavity-backed antenna with taper-based micro-strip SIW transition feeding. For radio transmission, a circular slot is etched on top of the SIW cavity. For optimal antenna design, the slot is etched slightly away from the cavity center to generate circularly polarized waves. Simulations show a wide axial ratio bandwidth of 7.860% between 11.02 GHz and 11.806 GHz. Experimental results confirm a similar wide axial ratio bandwidth of 4.9% between 10.8 GHz and 11.35 GHz. An SIW feed from an inductive window excites the radiating circular slot, resulting in a simulated wide impedance range of 1.548 GHz (10.338 GHz-11.886 GHz) and bandwidth of 13.93%. Experimental results show a wide impedance of 2.08 GHz (10.2 GHz-12.08 GHz) and bandwidth of 18.84%. The SIW cavity-backed antenna creates a unidirectional pattern, leading to gains of 6.61 dBi and 7.594 dBi in simulations and experiments, respectively. The proposed antenna was fabricated on a Rogers RT/Duroid 5880 substrate, and the reflection coefficient, radiation patterns, and gains were tested and compared using a computer simulator. The developed broadband antenna seems suitable for X-band applications.

• Restorative Dentistry and Endodontics
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• v.19 no.1
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• pp.231-254
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• 1994

Fracture of cusp, on posterior teeth, especially those carious or restored, is major cause of tooth loss. Inappropriate treatments, such as unnecessarily wide cavity preparations, increase the potential of further trauma and possible fracture of the remaining tooth structures. Fracture potential may be directly related to the stresses exerted upon the tooth during masticatory function. The purpose of this study is to evaluate the fracture resistance of tooth, restored with composite resin inlay. In this study, MOD inlay cavity prepared on maxillary first premolar and restored with composite resin inlay. Three dimensional finite element models with eight nodes isoparametric solid element, developed by serial grinding-photographing technique. These models have various occlusal isthmus and depth of cavity, 1/2, 1/3 and 1/4 of isthmus width and 0.7, 0.85 and 1.0 of depth of cavity. The magnitude of load was 474 N and 172 N as presented to maximal biting force and normal chewing force. These loads applied onto ridges of buccal and lingual cusp. These models analyzed with three dimensional finite element method. The results of this study were as follows : 1. There is no difference of displacement between width of occlusal isthmus and depth of cavity. 2. The stress concentrated at bucco-mesial comer, bucco-disal comer, pulpal line angle and the interface area between internal slopes of cusp and resin inlay. 3. The vector of stress direct to buccal and lingual side from center of cavity, to tooth surface going on to enamel. The magnitude of vector increase from occlusal surface to cervix. 4. The crack of tooth start interface area, between internal slop of buccal cusp and resin inlay. It progresses through buccopulpal line angle to cervix at buccomesial and buccodistal comer. 5. The influence with depth of cavity to fracture of tooth was more than width of isthmus. 6. It would be favorable to make the isthmus width narrower than a third of the intercuspal distance and depth of cavity is below 1 : 0.7.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1951-1956
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• 2008

Various MEMS accelerometers are used in engineering applications including automobiles, mobile phones, military systems, and electronic devices. Among them, the thermal accelerometer employing the temperature difference induced by the convective flow inside the micro cavity has been a topic of interest. As the convective sensor does not utilize a solid proof mass, it is compact, lightweight, inexpensive to manufacture, sensitive and highly endurable to mechanical shock. However, the complexity of the convective flow and various design constraints make optimization of a device a crucial step before fabrication. In this work, optimization of a 2-axis thermal convective MEMS accelerometer is conducted based on 3-dimensional numerical simulation. Parametric studies are performed by varying the several design variables such as the heater shape/size, the cavity size and types of the gas medium and the position of temperature probes in the sensor. The results of optimal design are presented.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.97-103
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• 2000

Gas pulsation discharged from the cylinder causes noise in the rotary compressor. Mufflers are usually used to reduce the noise generated by the gas pulsation. The muffler has been designed to maximize the acoustic transmission loss of the muffler. The gas which went through muffler is discharged to the cavity in compressor. Thus, the acoustic characteristics of cavity should be taken into account in muffler design. In this paper, the program for the acoustic substructure synthesis method is developed. This program can be interfaced with SYSNOISE which is commercial acoustic package. Several types of mufflers designed to have the better acoustic performance are suggested in this work and compared with the existing commerical muffler in the compressor. The acoustic performance of mufflers taking into consideration of the cavity in the compressor is also carried out by the developed program.

• Journal of Powder Materials
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• v.13 no.6 s.59
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• pp.455-461
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• 2006

High temperature dielectric constants of the various ceramic materials have been measured using cavity perturbation method. The measurements were applied to refractory, traditional and fine ceramic powder compacts from room temperature to $1200^{\circ}C$. Calibration constant in the equation suggested by Hutcheon et al., was determined from the dielectric constants of reference specimen (teflon and alumina) at room temperature. From these results, informations on the refectory materials were obtained for the microwave kiln design and understanding of the microwave heating effects of ceramics have been improved.

• Journal of radiological science and technology
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• v.20 no.1
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• pp.29-34
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• 1997

For radiological test in soft tissue or neighboring part with same signal intensity, proper test method and equipment shall be selected as needed. In case of female pelvic cavity, ultrasonography or computed tomography alternatively used, but MRI can be more usefully applied to design treatment method or operation plan by improving the diagnostic accuracy and careful observation of lesion characteristics. Magnetic Resonance Imaging using recently developed Enteral MRI contrast media can acquire more diagnostic information than using only intravenous contrast media. Thus this study attempted to examine the utility of anatomic structure and diagnostic acquisition by imaging the female pelvic cavity using Enteral MRI contrast media. As a result of analyzing magnetic resonance Imaging after administering Enteral MRI contrast media to pelvic cavity suspect patients, more diagnostic information media could be acquired than only using Intravenous contrast. Expecially, in the diagnosis of lesion position, shape, distinction from neighboring tissues it is thought that external Enteral MRI contrast media should be used.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.14-21
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• 2010

Fiber ring laser based intra-cavity absorption spectroscopic sensor has great potential for high sensitivity gas detection. Using the rate equations and propagation equations, we investigated theoretically factors that affect the sensitivity of such fiber ring laser sensors and determined the optimal design parameters and conditions for significant enhancement of the system sensitivity. Experiments have been conducted to determine the sensitivity enhancement performance. The results showed a factor of 25 ~ 30 in sensitivity enhancement in the experimental system, agreeing well with the theoretical expectations. Experiments on acetylene detection have also been carried out and the results showed that the ring cavity significantly increases the signal absorption and that high sensitivity can be obtained for gas detection.

• Geomechanics and Engineering
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• v.16 no.6
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• pp.569-575
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• 2018

The stability of shallow cavities with an arbitrary profile is a difficult issue in geotechnical engineering. This paper investigates this problem on the basis of the upper bound theorem of limit analysis and the Hoek-Brown failure criterion. The influence of pore pressure is taken into consideration by regarding it as an external force acting on rock skeleton. An objective function is constructed by equating the internal energy dissipation to the external force work. Then the Lagrange variation approach is used to solve this function. The validity of the proposed method is demonstrated by comparing the analytical solutions with the published research. The relations between shallow and deep cavity are revealed as well. The detaching curve of cavity roof with elliptical profile is obtained. In order to facilitate the application of engineering practice, the numerical results are tabulated, which play an important role in tunnel design and stability analysis of roof. The influential factors on potential collapse are taken into consideration. From the results, the impact of various factors on the extent of detaching is seen intuitively.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.91-99
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• 1995

An effort has been made to more accurately analyze the flow in the chip cavity, particularly to model the flow through the openings in the leadframe and correctly treat the thermal boundary condition at the leadframe. The theoretical analysis of the flow has been done by using the Hele- Shaw approximation in each cavity separated by a leadframe. The cross-flow through the openings in the leadframe has been incorporated into the Hele-Shaw formulation as a mass source term. The temperature of the leadframe has been calculated based on energy balance in the leadframe. The flow behavior in the leadframe has been verified experimentally. In the experiment, a transparent mold and clear fluid have been used for flow visualization. Comparisons were made between the calculation and experimental results which showed a good agreement.