• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.353-356
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• 2001

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. PON architecture is very simple but it requires MAC protocol for control of upstream traffic. This paper proposes a MAC protocol for a broadband access network using an ATM Passive Optical Network supporting CBR/rtVBR, nrtVBR, UBR and ABR traffic. For the proposed MAC scheme, we present grant field format, minislot format, and bandwidth allocation algorithm. from the simulation result, we have confirmed that our proposed scheme ran reduce the average tell delay in comparison to that of conventional MAC schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1B
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• pp.18-26
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• 2003

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network PON architecture is very simple but it requires MAC protocol for control of upstream traffic This paper proposes a Request-Counter MAC protocol for a broadband access network using an ATM Passive Optical Network supporting CBR/rtVBR, nrtVBR, UBR and ABR traffic For the proposed MAC scheme, we present Grant Field format, Minislot format, and bandwidth allocation algorithm From the simulation result, we have confirmed that our proposed scheme can reduce the average cell delay in comparison to that of conventional MAC schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.603-611
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• 2013

In this paper, we propose a new frame structure and the underlying dynamic resource control mechanism to support an integrated service, including a real-time (RT) service that requires to serve the end-to-end delay performance, as well as non-real-time (NRT) service, using Self-Organizing Time Division Multiple Access (SO-TDMA)-based MAC protocol in a multi-hop ad-hoc maritime communication network. The underlying frame structure is dynamically configured by resource allocation to guarantee the average target outage performance of the real-time service. Toward this end, we analyze the average outage probability and its performance is verified for the proposed frame structure by simulation.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1635-1636
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• 2006

In this paper, a non-vacuum packaged single crystalline silicon MEMS gyroscope is designed, fabricated and tested. To reduce air damping of the gyroscope structure for non-vacuum packaging, air damping model is used and damping is minimized by analysis. The inner and outer spring length is optimized by ANSYS simulation for rigid body motion. The gyroscope is fabricated by SiOG(Silicon On Glass) process. The performance of the gyroscope is measured to evaluate the characteristic of the gyroscope. The sensitivity, non-linearity, noise density and the bias stability are measured to 9.7693 mV/deg/s, 04265 %, 2.3 mdeg/s/rtHz and 16.1014 deg/s, respectively.

• Korean Journal of Metals and Materials
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• v.48 no.3
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• pp.187-193
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• 2010

The solute carbon content in ferrite is one of the important factors to obtain good formability in low carbon steels. Although most of the carbons are consumed by the formation of grain boundary cementite during coiling after hot-rolling, the carbon content after coiling is normally observed much more than that of equilibrium. In this study, a classical nucleation and growth model is used to simulate the precipitation kinetics of the grain boundary cementite from coiling temperature (CT) to room temperature (RT). The predicted precipitation behaviors depending on the initial carbon content and the cooling rate are compared with the reported. As a result, the lateral growth of thickening of cementite is a major factor for the sluggish reaction of grain boundary cementite. The reduction of solute carbon content after coiling is divided into three regions: a) increase due to no cementite precipitation, b) decrease due to the fast length-wise growth of cementite, c) increase due to the slow thickness-wise growth of cementite.

• Journal of the Korean Vacuum Society
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• v.6 no.S1
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• pp.70-74
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• 1997

The study of the thickness dependence of the electron energy structure of Fe, Ni, Ti and Zr sublayers in Ni/Ti and Fe/Zr multilayers by using the experimental and computer simulated optical spectroscopy has been performed. A series of Ni/Ti and Fe/Ze multiayered films (MLF) with a bilayer period of 0.5 - 30 nm and constant (Ni/Ti) / different (Fe/Zr) sublayer thickness ratios were prepared by using computer-controlled double-pair target face-to-face sputtering onto a glass substrate at room temperature (RT) Computer simulation of the resulting optical properties of these MLF was carried out by solving of multireflection problem with a matrix method assuming either "sharp" interfaces resulting in rectangular depth profiles of the components or "mixed" (alloy-like) interfaces of variable thickness between pure-metal sublayers. Optical constants of pure bulk metals as well as equiatomic alloy interfaces were employed in these simulations. It was shown that the difference between experimental and simulated optical properties of the investigated MLF increases with decrease in sublayer thickness. This result allows to conclude that the electronic structures of sublayers below 4-5 nm thickness in mlf differ from the corresponding bulk metals.ponding bulk metals.

• The Journal of Korean Society for Radiation Therapy
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• v.20 no.1
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• pp.25-29
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• 2008

Purpose: To monitor the changes of location of prostate gland using DIPS and to examine the adjustment and proton beam therapy depending on the movement of prostate gland in proton beam therapy for prostate gland in which a fiducial gold marker was inserted. Materials and Methods: This study was conducted in ten patients with prostate cancer who received proton beam therapy since April of 2008. To monitor the change of prostate location, three fiducial gold markers were inserted prior to the treatment. To minimize the movement of prostate gland, patients were recommended to urinate prior to the treatment, to intake a certain amount of water and to concomitantly undergo rectal balloon. In these patients, the set-up position was identical to that for a CT-simulation. The PA (posterior-anterior) and lateral images were obtained using both DIPS (digital image positioning system) and a plain radiography, and they were compared between the two imaging modalities. Thus, the changes of the location of fiducial gold marker were assessed based on three coordinates (x, y, z) and then adjusted. This was followed by proton beam therapy. Results: Images which were taken using a plain radiography were compared with those which were taken using DIPS. In ten patients, according to a reference bony marker, the mean changes of the location of fiducial gold marker based on an iso-center were X-axis: $\pm$0.116 cm, Y-axis: $\pm$0.19 cm and Z-axis: $\pm$0.176 cm. These ten patients showed a difference in the changes of location of prostate gland and it ranged between RT: 0.04 cm and RT: 0.24 cm on the X-axis; between Inf: 0.03 cm and Sup: 0.42 cm on the Y-axis; and Post: 0.05 cm and Ant: 0.35 cm on the Z-axis. Conclusion: To minimize the movement of prostate gland, as the pre-treatment prior to the treatment. In all the patients, however, three fiducial gold markers showed a daily variation which were inserted in the prostate gland. Based on the above data, Thus, the requirement of gold marker matching system depending on the daily variation in the proton beam therapy for which more accurate establishment of target was confirmed. It is assumed that an accurate effect of proton beam therapy would be enhanced by adjusting the target-center depending on the location change of prostate gland using DIPS which was used in the current study.

• The Journal of Korean Society for Radiation Therapy
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• v.1 no.1
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• pp.70-78
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• 1985

The intrauterine irradiation is essential to achieve adequate tumor dose to centeral tumor mass in radio therapy for uterine malignancy. The complications of pelvic organ are known to be directly related to radiation dose and physical parameters. The comparison study of currently using 2 systems was undertaken. The simulation films and medical records of 135 patients who was treated with intrauterine irradiation at one of general hospitals in Busan and Seoul between Jan. 1983 and June 1983, were critically analized and physical parameters of low dose rate system and remote controlled high dose rate system were measured. The physical parameters include distances between lateral walls of vaginal fornices, longitudinal and lateral angles of tandem to the body axis, the distance from the external os of uterine cervix to the central axis of ovoids, the radiation dose ratio to rectum and bladder to reference point A. Followings were summary of study results: 1. In distances between lateral walls of vaginal fornices the low dose rate system showed wide distribution and relatively larger distances. In low dose rate system 5.0-5.9 cm was $55.89\%$ 6.0-6.9 cm: $23.53\%$, 4.0-4.9cm: $10.29\%$, 3.0-3.9cm: $10.29\%$, and in high dose rate system 5.0-5.9cm was $80.59\%$, 4.0-4.9cm: $17.91\%$, $6.0\~6.9\;cm:\;1.5\%$. 2. In lateral angulation of tandem to body axis, the low does system revealed mid position (the position along body axis) $64.7\%$, Lt. deviation $19.13\%$ and Rt. deviation $16.17\%$. However the high dose rate system revealed mid position $49.26\%$ Lt. deviation $40.29\%$ and Rt. deviation $10.45\%$. 3. In longitudinal angulation of tandem to body axis the mid position was $11.77\%$ and anterior angulation $88.23\%$ in low dose rate system but in high dose rate system the mid position was $1.56\%$ and anterior angulation $98.44\%$. 4. Down ward displacement of ovoids below external os was only $2.94\%$ in low dose rate system and $67.69\%$ in high dose rate system. 5. The radiation dose ration to rectum to reference point A was $102.70\%$ in high dose rate system and $70.09\%$ in low dose rate system. The dose ratio to bladder to reference point A was $78.14\%$ in high dose rate system and $75.32\%$ in low dose rate system.

• The Journal of Korean Society for Radiation Therapy
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• v.31 no.2
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• pp.13-24
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• 2019

Purpose: CT scan range is insufficient for various reasons in head and neck Tomotherapy^®. To solve that problem, Re-CT simulation is good because CT scan range affects accurate dose calculations, but there are problems such as increased exposure dose, inconvenience, and a change in treatment schedule. We would like to evaluate the minimum CT scan range required by changing the plan setup parameter of the existing CT scan range. Materials and methods: CT Simulator(Discovery CT590 RT, GE, USA) and In House Head & Neck Phantom are used, CT image was acquired by increasing the image range from 0.25cm to 3.0cm at the end of the target. The target and normal organs were registered in the Head & Neck Phantom and the treatment plan was designed using ACCURAY Precision^®. Prescription doses are Daily 2.2Gy, 27 Fxs, Total Dose 59.4Gy. Target is designed to 95%~107% of prescription dose and normal organ dose is designed according to SMC Protocol. Under the same treatment plan conditions, Treatment plans were designed by using five methods(Fixed-1cm, Fixed-2.5cm, Fixed-5cm, Dynamic-2.5cm Dynamic-5cm) and two pitches(0.43, 0.287). The accuracy of dose delivery for each treatment plan was analyzed by using EBT3 film and RIT(Complete Version 6.7, RIT, USA). Results: The accurate treatment plan that satisfying the prescribed dose of Target and the tolerance dose in normal organs(SMC Protocol) require scan range of at least 0.25cm for Fixed-1cm, 0.75cm for Fixed-2.5cm, 1cm for Dynamic-2.5cm, and 1.75cm for Fixed-5cm and Dynamic-5cm. As a result of AnalysisAnalysis by RIT. The accuracy of dose delivery was less than 3% error in the treatment plan that satisfied the SMC Protocol. Conclusion: In case of insufficient CT scan range in head and neck Tomotherapy^®, It was possible to make an accurate treatment plan by adjusting the FW among the setup parameter. If the parameter recommended by this author is applied according to CT scan range and is decide whether to re-CT or not, the efficiency of the task and the exposure dose of the patient are reduced.

• Radiation Oncology Journal
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• v.21 no.1
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• pp.100-106
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• 2003

Purpose : To develop a patients' setup verification tool (PSVT) to verify the alignment of the machine and the target isocenters, and the reproduclbility of patients' setup for three dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT). The utilization of this system is evaluated through phantom and patient case studies. Materials and methods : We developed and clinically tested a new method for patients' setup verification, using digitally reconstructed radiography (DRR), simulation, porial and digital images. The PSVT system was networked to a Pentium PC for the transmission of the acquired images to the PC for analysis. To verify the alignment of the machine and target isocenters, orthogonal pairs of simulation images were used as verification images. Errors in the isocenter alignment were measured by comparing the verification images with DRR of CT Images. Orthogonal films were taken of all the patients once a week. These verification films were compared with the DRR were used for the treatment setup. By performing this procedure every treatment, using humanoid phantom and patient cases, the errors of localization can be analyzed, with adjustments made from the translation. The reproducibility of the patients' setup was verified using portal and digital images. Results : The PSVT system was developed to verify the alignment of the machine and the target isocenters, and the reproducibility of the patients' setup for 3DCRT and IMRT. The results show that the localization errors are 0.8$\pm$0.2 mm (AP) and 1.0$\pm$0.3 mm (Lateral) in the cases relating to the brain and 1.1$\pm$0.5 mm (AP) and 1.0$\pm$0.6 mm (Lateral) in the cases relating to the pelvis. The reproducibility of the patients' setup was verified by visualization, using real-time image acquisition, leading to the practical utilization of our software Conclusions : A PSVT system was developed for the verification of the alignment between machine and the target isocenters, and the reproduclbility of the patients' setup in 3DCRT and IMRT. With adjustment of the completed GUI-based algorithm, and a good quality DRR image, our software may be used for clinical applications.