• Radiation Oncology Journal
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• v.27 no.1
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• pp.42-48
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• 2009

Purpose: The introduction of image guided radiation therapy/four-dimensional radiation therapy (IGRT/4DRT) potentially increases the accumulated dose to patients from imaging and verification processes as compared to conventional practice. It is therefore essential to investigate the level of the imaging dose to patients when IGRT/4DRT devices are installed. The imaging dose level was monitored and was compared with the use of pre-IGRT practice. Materials and Methods: A four-dimensional CT (4DCT) unit (GE, Ultra Light Speed 16), a simulator (Varian Acuity) and Varian IX unit with an on-board imager (OBI) and cone beam CT (CBCT) were installed. The surface doses to a RANDO phantom (The Phantom Laboratory, Salem, NY USA) were measured with the newly installed devices and with pre-existing devices including a single slice CT scanner (GE, Light Speed), a simulator (Varian Ximatron) and L-gram linear accelerator (Varian, 2100C Linac). The surface doses were measured using thermo luminescent dosimeters (TLDs) at eight sites-the brain, eye, thyroid, chest, abdomen, ovary, prostate and pelvis. Results: Compared to imaging with the use of single slice non-gated CT, the use of 4DCT imaging increased the dose to the chest and abdomen approximately ten-fold ($1.74{\pm}0.34$ cGy versus $23.23{\pm}3.67$cGy). Imaging doses with the use of the Acuity simulator were smaller than doses with the use of the Ximatron simulator, which were $0.91{\pm}0.89$ cGy versus $6.77{\pm}3.56$ cGy, respectively. The dose with the use of the electronic portal imaging device (EPID; Varian IX unit) was approximately 50% of the dose with the use of the L-gram linear accelerator ($1.83{\pm}0.36$ cGy versus $3.80{\pm}1.67$ cGy). The dose from the OBI for fluoroscopy and low-dose mode CBCT were $0.97{\pm}0.34$ cGy and $2.3{\pm}0.67$ cGy, respectively. Conclusion: The use of 4DCT is the major source of an increase of the radiation (imaging) dose to patients. OBI and CBCT doses were small, but the accumulated dose associated with everyday verification need to be considered.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.3
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• pp.71-76
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• 2017

The electrical behavior and flexibility of the screen printed Ag circuits were investigated with infrared radiation sintering times and sintering temperatures. Electrical resistivity and radio frequency characteristics were evaluated by using the 4 point probe measurement and the network analyzer by using cascade's probe system, respectively. Electrical resistivity and radio frequency characteristics means that the direct current resistance and signal transmission properties of the printed Ag circuit. Flexibility of the screen printed Ag circuit was evaluated by measuring of electrical behavior during IPC sliding test. Failure mode of the Ag printed circuits was observed by using field emission scanning electron microscope and optical microscope. Electrical resistivity of the Ag circuits screen printed on Pl substrate was rapidly decreased with increasing sintering temperature and durations. The lowest electrical resistivity of Ag printed circuit was up to $3.8{\mu}{\Omega}{\cdot}cm$ at $250^{\circ}C$ for 45 min. The crack length arisen within the printed Ag circuit after $10{\times}10^4$ sliding numbers was 10 times longer than that of after $2.5{\times}10^4$ sliding numbers. Measured insertion loss and calculated insertion loss were in good agreements each other. Insertion loss of the printed Ag circuit was increased with increasing the number of sliding cycle.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.6
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• pp.1154-1162
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• 2016

This paper proposes a fast-transient digital LDO(Low dropout) regulator with binary-weighted current control technique. Conventional digital LDO takes a long time to stabilize the output voltage, because it controls the amount of current step by step, thus ringing problem is generated. Binary-weighted current control technique rapidly stabilizes output voltage by removing the ringing problem. When output voltage reliably reaches the target voltage, It added the FRZ mode(Freeze) to stop the operation of digital LDO. The proposed fast response digital LDO is used with a slow response DC-DC converter in the system which rapidly changes output voltage. The proposed digital controller circuit area was reduced by 56% compared to conventional bidirectional shift register, and the ripple voltage was reduced by 87%. A chip was implemented with a $0.18{\mu}F$ CMOS process. The settling time is $3.1{\mu}F$ and the voltage ripple is 6.2mV when $1{\mu}F$ output capacitor is used.

• Progress in Medical Physics
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• v.17 no.3
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• pp.144-152
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• 2006

The telemedicine using independent client-server system via networks can provide high quality normalized services to many hospitals, specifically to local/rural area hospitals. This will eventually lead to a decreased medical cost because the centralized institute can handle big computer hardware systems and complicated software systems efficiently and economically, Customized cancer radiation treatment planning for each patient Is very useful for both a patient and a doctor because it makes possible for the most effective treatment with the least possible dose to patient. Radiation planners know that too small a dose to the tumor can result in recurrence of the cancer, while too large a dose to healthy tissue can cause complications or even death. The best solution is to build an accurate planning simulation system to provide better treatment strategies based on each patient's computerized tomography (CT) image. We are developing a web-based and a network-based customized cancer radiation therapy simulation system consisting of four Important computer codes; a CT managing code for preparing the patients target data from their CT image files, a parallel Monte Carlo high-energy beam code (PMCEPT code) for calculating doses against the target generated from the patient CT image, a parallel linear programming code for optimizing the treatment plan, and scientific data visualization code for efficient pre/post evaluation of the results. The whole softwares will run on a high performance Beowulf PC cluster of about 100-200 CPUs. Efficient management of the hardware and software systems is not an easy task for a hospital. Therefore, we integrated our system into the client-sewer system via network or web and provide high quality normalized services to many hospitals. Seamless communication with doctors is maintained via messenger function of the server-client system.

• Journal of Energy Engineering
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• v.8 no.2
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• pp.298-308
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• 1999

Experimental study on characteristics of direct contact condensation of steam discharged into a sub-cooled water pool has been performed using five different sizes of horizontal nozzle over a wide range of steam mass fluxes and pool temperatures. Steam condensation phenomena have been observed visually and by taking pictures of steam jets using a high speed video camera. Two different steam jet shapes such as ellipsoidal shape and conical shape were typically observed for a stable steam jet, depending on the steam mass flux and pool temperature. The steam jet expansion ratio and the steam jet length as well as the condensation heat transfer coefficients were determined. The effect of steam mass flux, pool temperature, and nozzle diameter on these parameters were also discussed. Empirical correlations for the steam jet lengths and the condensation heat transfer coefficients as a function of steam mass flux and condensation driving potential were established. The axial and radial temperature distributions in steam jet and in surrounding water were measured. The effect of steam mass flux, pool temperature, and nozzle diameter were also discussed. The condensation regime map, which consists of six regimes such as chugging, transient chugging, condensation oscillation, stable condensation, bubble condensation oscillation, and intermittent oscillation condensation, were established. In addition, the dynamic pressures at the pool wall were measured. The close relation of dynamic pressure and steam condensation mode, which is also dependent on steam mass flux and pool temperature, was found.

• Journal of Sensor Science and Technology
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• v.9 no.2
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• pp.96-105
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• 2000

Fiber optic TR-EFPI(total reflected extrtinsic Fabry-Perot interferometric) sensor was developed to measure the strain of structures, such as building, bridge, aircraft, etc. It has been difficult to distinguish the increase and decrease of the strain from the conventional fiber optic EFPI sensor because their signals only have a sinusoidal wave pattern related to the change of strain. Also, the absolute strain could not be measured by the simple fiber optic EFPI sensor. In this study, in order to measure the magnitude of strain with the direction of strain, the fiber optic sensor was simply constructed with the total reflected EFPI sensor probe. This probe was manufactured with a single mode fiber and a mirror coated fiber in a silica glass capillary tube. The output signal of this fiber optic TR-EFPT sensor can give the information about the magnitude and the direction of strain. The loading-unloading test was performed by the universal testing machine with alluminum beam specimen to compare the strain from fiber optic TR-EFPI sensor with the value from electrical strain gauge. In the result of this experiment. the strain from fiber optic TR-EFPI sensor had a good agreement with the values from the electrical strain gauge.

• The Journal of the Acoustical Society of Korea
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• v.30 no.1
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• pp.56-62
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• 2011

In the present study, the phase velocities of guided ultrasonic waves such as the first arriving signal (FAS) and the slow guided wave (SGW) propagating along the long axis on the 12 tubular cortical bone samples in vitro were measured and their correlations with the cortical thickness were investigated. The phase velocities of the FAS and the SGW were measured by using the axial transmission method in air with a pair of unfocused ultrasonic transducers with a diameter of 12.7 mm and a center frequency of 200 kHz. The phase velocity of the FAS measured at 200 kHz exhibited a very high negative correlation with the cortical thickness and that of the SGW arriving after the FAS showed a high positive correlation with the cortical thickness. The simple and multiple linear regression models with the phase velocities of the FAS and the SGW as independent variables and the cortical thickness as a dependent variable revealed that the coefficient of determination of the multiple linear regression model was higher than those of the simple linear regression models. The phase velocities of the FAS and the SGW measured at 200 kHz on the 12 tubular cortical bone samples were, respectively, consistent with those of the S0 and the A0 Lamb modes calculated at 200 kHz on the cortical bone plate.

• Journal of the Korean Society for Advanced Composite Structures
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• v.3 no.1
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• pp.29-34
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• 2012

Even though the longitudinally stiffened laminated composite plates with closed section ribs should be an effective system for axially compressed members, the existing researches on the applications of closed-section ribs, especially for the laminated composite plates, are not sufficient. This study is aimed to examine the influence of the sectional stiffness of U-shaped ribs on the buckling modes and strengths of laminated composite plates. Applying the orthotropic plates with eight layers of the layup $[(0^{\circ})_4]_s$ and $[(0^{\circ}/90^{\circ})_2]_s$, 3-dimensional finite element models for the U-rib stiffened plates were setup by using ABAQUS and then a series of eigenvalue analyses were conducted. From the parametric studies, the minimum required ply thicknesses as well as the buckling strengths were presented for the analysis models. The buckling strengths were compared with the theoretical critical stress equation for simply supported plates based on the Classical laminated plate theory. This study will contribute to the future study for evaluating the minimum required stiffness and optimum design of U-rib stiffened plates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.5
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• pp.527-534
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• 2015

This paper presents an integrated chassis control with electronic stability control (ESC) and active front steering (AFS) under lateral force constraint on AFS. The control yaw moment is calculated using a sliding mode control. The tire forces generated by ESC and AFS are determined using weighted pseudo-inverse based control allocation (WPCA) in order to generate the control yaw moment. On a low friction road, AFS is not effective when the lateral tire forces of front wheels are easily saturated. To solve problem, the lateral force of AFS is limited to its maximum and the braking of ESC is applied with WPCA. To evaluate the effectiveness of the proposed method, a simulation was performed on the vehicle simulation package, $CarSim^{(R)}$. From the simulation, it was verified that the proposed method could enhance the maneuverability and lateral stability if the lateral force of AFS exceeds its maximum.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.12 no.2
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• pp.103-111
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• 1979

For the effective utilization of the coastal fish resources in Korea, an investigation on the optimum processing conditions and the quality of a textured fish protein concentrate similar to the texture of animal meat has been carried out with the fish meat of Alaska pollack and mackerel. A noodle shaped product was prepared with the fish meat paste after the adjustment of pH and salt content. The product was soaked in $96\%$ ethyl alcohol to produce textured fish protein concentrate and then dried. The processing conditions were estimated with the rehydration capacity of the textured fish protein concentrate(FFC). The quality of the final product was evaluated with chemical composition, sensory test and texture measurement. The optimum pH and salt content of the fish meat for the processing of meaty textured FPC were 7.5 and $1.0\%$ respectively. The most effective soaking conditions were as follows:soaking time, 40 min. ; temperature of alcohol, 5 to $20^{\circ}C$;amount of alcohol, 4 times the weight of tile fish meat paste, number of soaking in alcohol, 4 times. The alcohol remaining in meaty textured FPC could be removed effectively by forced air drying. The yield and the contents of protein and lipid in the meaty textured FPC from Alaska pollack were $19.9\%\;84.3\%\;and\;0.5\%$ and those from mackerel were $29.8\%,\;78.1\%\;and\;3.6\%$ respectively. The content of essential amino acid in the meaty textured FPC from Alaska pollack and mackerel was not inferior to that of beef, textured soybean protein and FAO pattern. Beef meat can be substituted with the meaty textured FPC up to $50\%$ in processing meat balls withoutanysignificantlossinthetaste, ordor and texture.