• Proceedings of the KSME Conference
• /
• 2003.04a
• /
• pp.1754-1759
• /
• 2003

Two-dimensional flow over a pair of circular cylinders in side-by-side arrangements at low Reynolds numbers has been numerically investigated in this study. Numerical simulations are performed, using the immersed boundary method, in the ranges of $40{\leq}Re{\leq}160$ and $g^{\ast}<5$, where Re and $g^{\ast}$ are, respectively, the Reynolds number and the spacing between the two cylinder surfaces divided by the cylinder diameter. Results show that total six kinds of wake patterns are observed over the ranges: antiphase-synchronized, inphase-synchronized, flip-flopping, single bluff-body, deflected, and steady wake patterns. It is found that the characteristics of the flow significantly depends both on the Reynolds number and gap spacing, with the latter much stronger than the former. Instantaneous flow fields, time traces, flow statistics and so on are presented to identify the wake patterns and then to understand the underlying mechanism. It is remarkable that, for the deflected wake pattern, the gap flow is deflected invariably to the cylinder of higher drag coefficient and the deflection way does not change at all. Moreover, the bifurcation phenomena where either of two wake patterns can occur are found at certain flow conditions.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.27 no.7
• /
• pp.909-919
• /
• 2003

Two-dimensional flow over a pair of circular cylinders in a side-by-side arrangement at low Reynolds numbers has been numerically investigated in this study Numerical simulations are performed, using the immersed boundary method, for the ranges of 40$\leq$Re$\leq$160 and $g^{*}$＜5, where Re and $g^{*}$ are, respectively, the Reynolds number and the spacing between the two cylinder surfaces divided by the cylinder diameter. Results show that a total of six kinds of wake patterns are observed over the ranges: antiphase-synchronized, inphase-synchronized, flip-flopping, single bluff-body, deflected, and steady wake patterns. It is found that the characteristics of the flow significantly depends both on the Reynolds number and gap spacing, with the latter much stronger than the former. Instantaneous flow fields, time traces, flow statistics and so on are presented to identify the wake patterns and then to understand the underlying mechanism. Moreover, the bifurcation phenomenon where either of two wake patterns can occur is found at certain flow conditions.ons.

• The Journal of Korean Society for Radiation Therapy
• /
• v.34
• /
• pp.61-72
• /
• 2022

Purpose: Conventional CBCT(Cone-beam Computed-tomography) caused an error in the target volume due to organ movement in the area affected by respiratory movement. The purpose of this paper is to evaluate the usefulness of accuracy and time spent using the Gated CBCT function, which reduces errors when performing RGRT(respiratory gated radiation therapy), and to examine the appropriateness of phase. Materials and methods: To evaluate the usefulness of Gated CBCT, the QUASAR^TM respiratory motion phantom was used in the Truebeam STx^TM. Using lead marker inserts, Gated CBCT was scaned 5 times for every 20~80% phase, 30~70% phase, and 40~60% phase to measure the blurring length of the lead marker, and the distance the lead marker moves from the top phase to the end of the phase was measured 5 times. Using Cedar Solid Tumor Inserts, 4DCT was scanned for every phase, 20-80%, 30-70%, and 40-60%, and the target volume was contoured and the length was measured five times in the axial direction (S-I direction). Result: In Gated CBCT scaned using lead marker inserts, the axial moving distance of the lead marker on average was measured to be 4.46cm in the full phase, 3.11cm in the 20-80% phase, 1.94cm in the 30-70% phase, 0.90cm in the 40-60% phase. In Fluoroscopy, the axial moving distance of the lead marker on average was 4.38cm and the distance on average from the top phase to the beam off phase was 3.342cm in the 20-80% phase, 3.342cm in the 30-70% phase, and 0.84cm in the 40-60% phase. Comparing the results, the difference in the full phase was 0.08cm, the 20~80% phase was 0.23cm, the 30~70% phase was 0.10cm, and the 40~60% phase was 0.07cm. The axial lengths of ITV(Internal Target Volume) and PTV(Planning Target Volume) contoured by 4DCT taken using cedar solid tumor inserts were measured to be 6.40cm and 7.40cm in the full phase, 4.96cm and 5.96cm in the 20~80% phase, 4.42cm and 5.42cm in the 30~70% phase, and 2.95cm and 3.95cm in the 40~60% phase. In the Gated CBCT, the axial lengths on average was measured to be 6.35 cm in the full phase, 5.25 cm in the 20-80% phase, 4.04 cm in the 30-70% phase, and 3.08 cm in the 40-60% phase. Comparing the results, it was confirmed that the error was within ±8.5% of ITV Conclusion: Conventional CBCT had a problem that errors occurred due to organ movement in areas affected by respiratory movement, but through this study, obtained an image similar to the target volume of the setting phase using Gated CBCT and verified its usefulness. However, as the setting phase decreases, the scan time was increases. Therefore, considering the scan time and the error in setting phase, It is recommended to apply it to patients with respiratory coordinated stereotactic radiation therapy using a wide phase of 30-70% or more.

• Korean Journal of Logic
• /
• v.2
• /
• pp.35-61
• /
• 1998

개최들의 개별화를 위한 대표적인 법칙으로 간주되고 있는 라이프니츠의 법칙은 철학에서만 아니라 수학이나 논리학과 같은 순수과학에서도 중요한 법칙으로 사용되고 있다. 그러나 최근에 들어서 라이프니츠의 법칙은 그 논리적 위상과 관련하여 심각한 논란의 대상이 되고 있다. 이러한 논란의 근본적 원인은 칸트나 블랙과 같은 철학자들에 의해 라이프니츠의 법칙이 적용되지 않을 기능성을 보이는 반례가 제시되었고, 많은 철학자들이 이에 동조한 데에서 찾을 수 있다. 라이프니츠의 법칙의 논리적 위상과 관계된 철학자들의 입장은 크게 두 가지로 구분된다. 첫 번째 입장은 블랙 등에 의해 제시된 예들을 라이프니츠의 법칙에 대한 정당한 반례로 간주하는 입장이고, 두 번째 입장은 이러한 예들은 리이프니츠의 법칙에 대한 반례로 간주될 수 없다는 입장이다. 두 번째 입장을 쥐이는 대표적 철학자는 헷킹이다. 헷킹은 시공간에 대한 인습주의에 입각하여 블랙 등에 의해 제시된 예는 완전한 가능성을 나타내는 것이 아니고 라이프니츠의 법칙은 가능세계에 대한 메타 원칙으로 간주되어야 한다고 주장하고 있다. 본고에서 필자는 리이프니츠의 법칙을 옹호하려는 헷킹의 시도는 성공적이지 못하고, 또한 블랙 등에 의해 제시된 예들은 라이프니츠의 법칙에 대안 정당한 반례로 간주되어야 한다는 입장을 개진하고 있다. 필자가 이러한 입장을 취하게 된 것은 헷킹의 입장은 논리적 기능성과 물리적 기능성 사이의 구별을 어렵게 한다는 문제점 이외에도 가능세계 의미론과 관련된 중요한 문제점들을 야기하고 있기 때문이다. 가능세계 의미론과 관련된 문제점은 이러한 시도는 가능세계 의미론에 입각한 양상명제들의 해석의 범위를 제한하게 만들고 De-Re 양상명제에 대한 해석을 위해 필수적인 헤세이티즘의 수용을 불가능하게 한다는 것이다.

• The Journal of Korean Society for Radiation Therapy
• /
• v.27 no.1
• /
• pp.73-78
• /
• 2015

Purpose : Under the assumption of change to the amplitude based sorting, the study will use four dimensional computed tomography imaging (4DCT) arrayed using the phase based sorting to analyze the respiratory phase difference. Materials and Methods : The study analyzed the 4DCT (4-dimensional computed tomography) images of 10 liver cancer patients that were treated with respiratory gated radiotherapy from 2015 February to March. Using RPM respiratory gating (RPM 1.7.5, Varian, USA) equipment, imaging according to respiratory cycle of phase based sorting was acquired and using a treatment planning system (Pinnacle 9.2, Philips, USA) the acquired imaging according to respiratory cycle was used to measure the abdominal movement value by respiratory cycle. The measuring point was the point where the center point of the Marker Block and the body surface met in the 50% phase image and here the coordinate values Lateral, Vertical, Longitudinal (X, Y, Z) were set as reference points, and on the X, Z plane identical to the reference point, using the identical method the Y axis coordinate value of each 0%, 30%, 40%, 50%, 60%, 80% phase images were acquired to quantitatively measure the variation of distance to the Y axis. The abdominal movement value according to respiration was applied to the theoretical model that the value decreases linearly from maximum inhalation to maximum exhalation to divide the variation of my value to predict as amplitude value by respiratory cycle and conversely the variation in amplitude was recalculated with the phase variation deviation value to analyze. Results : The deviation value between expected value and actual location was the largest in the 30% phase with 0.24 cm, and standard deviation was also the largest in 30% phase with 0.13 cm. The effective value of the deviation value derived from the average of the deviation squared value of each patient appeared as minimum 0.7 cm, maximum 0.18 cm, average 0.12 cm, and standard deviation 0.4 cm. Also by dividing the actual movement distance value with the peak expiration value then converting it into %Phase, the deviation value with actual phase 16.5% in 30% phase, 10.0% and 40% phase, 10.0% and 60% phase, 15.4% and 80% phase, and overall average about 13%, and arraying based on amplitude, phase shift occurred and further it was from peak expiration the chance of deviation occurrence was increasingly measured. Conclusion : Based on the results of the study there were differences between value acquired based on theoretical model and actual value. Therefore in respiratory gated radiotherapy using external surrogates, there needs to be establishment of respiration gated radiation system that avoids the combination of two Sorting methods considering that there will be occurrence of treatment and corresponding clinical differences due to the phase difference that occur due to the Amplitude based Phase Sorting.

• The Journal of Korean Society for Radiation Therapy
• /
• v.22 no.2
• /
• pp.113-122
• /
• 2010

Purpose: To evaluate the accuracy of a target position at static and dynamic state by using Dynamic phantom for the difference between tumor's actual movement during respiratory gated radiation therapy and skin movement measured by RPM (Real-time Position Management). Materials and Methods: It self-produced Dynamic phantom that moves two-dimensionally to measure a tumor moved by breath. After putting marker block on dynamic phantom, it analyzed the amplitude and status change depending on respiratory time setup in advance by using RPM. It places marker block on dynamic phantom based on this result, inserts Gafchromic EBT film into the target, and investigates 5 Gy respectively at static and dynamic state. And it scanned investigated Gafchromic EBT film and analyzed dose distribution by using automatic calculation. Results: As a result of an analysis of Gafchromic EBT film's radiation amount at static and dynamic state, it could be known that dose distribution involving 90% is distributed within margin of error of 3 mm. Conclusion: As a result of an analysis of dose distribution's change depending on patient's respiratory cycle during respiratory gated radiation therapy, it is expected that the treatment would be possible within recommended margin of error at ICRP 60.

• Journal of Ocean Engineering and Technology
• /
• v.33 no.2
• /
• pp.196-202
• /
• 2019

In this study, the excessive noise and vibration phenomena of a high-speed Ro/Ro passenger ship were analyzed, and a countermeasure was taken based on them. This ship was granted a comfort class notation by the classification society, which was COMFORT-VIBRATION-II and COMFORT-NOISE-CREW-II. However, unfortunately, excessive noise and vibration in the aft part of the ship were delivered from the twin shaft propellers, and therefore the Class Requirement was not satisfied before delivery. In order to obtain the class notation, all of the concerned parties came to an agreement to reduce the noise and vibration level during operation after delivery because a seasonal ferry service was already scheduled and the cabin was fully booked. The root cause of the massive amount of noise and vibration was mainly the propeller-induced excitation pulse and beating that occurred from the mismatch of the rotating speeds of the two shaft lines. A 1st order vibrating force and beating phenomena existed in the propeller. Thus, a reduction of the excitation force, elimination of the beating phenomena, and decrease of the noise level at the aft area cabins and public spaces were required. In addition, structural reinforcements were conducted using pillars and additional girders at the aft part of the decks.

• Journal of Korea Port Economic Association
• /
• v.38 no.3
• /
• pp.87-104
• /
• 2022

Considering the complex structure and high volatility in the shipping market, it is important to investigate the connectedness amongst influencing factors. This study explores the dynamic relationship between supply-demand factors and shipping freight indices. We choose Capesize and Panamax in the bulk carrier market and use quarterly data of GDP, world fleet, BCI, and BPI from 1999 to 2021. Applying the wavelet analysis and wavelet Granger causality test, the simultaneous examination of co-movement and causality between two factors and the shipping market in both the time and frequency domains is achieved. We find that co-movement and causality vary across time and frequencies, thereby existing dynamic relationships between variables. Second, compared to multiple coherencies using demand and supply factors together, partial coherencies indicate noticeable causalities. It implies that analyzing demand and supply factors separately is essential. Finally, shipping freight indices show a high correlation with the demand factor in a good market and with the supply factor in a bad market. Generally, GDP positively leads shipping freights in the recovery phase while the world fleet negatively leads shipping freights in the downturn. The research is meaningful in that the rarely-applied wavelet analysis is adopted in the shipping market and that it gives a reasonable ground to explain the role of supply and/or demand factors in different phases of the market cycle.

• The Journal of Korean Society for Radiation Therapy
• /
• v.30 no.1_2
• /
• pp.83-95
• /
• 2018

Purpose : After planning the Respiratory Gated Radiotherapy for Lung cancer, the movement and volume change of sparing normal structures nearby target are not often considered during dose evaluation. This study carried out 4-D dose evaluation which reflects the movement of normal structures at certain phase of Respiratory Gated Radiotherapy, by using Deformable Image Registration that is well used for Adaptive Radiotherapy. Moreover, the study discussed the need of analysis and established some recommendations, regarding the normal structures's movement and volume change due to Patient's breathing pattern during evaluation of treatment plans. Materials and methods : The subjects were taken from 10 lung cancer patients who received Respiratory Gated Radiotherapy. Using Eclipse(Ver 13.6 Varian, USA), the structures seen in the top phase of CT image was equally set via Propagation or Segmentation Wizard menu, and the structure's movement and volume were analyzed by Center-to Center method. Also, image from each phase and the dose distribution were deformed into top phase CT image, for 4-dimensional dose evaluation, via VELOCITY Program. Also, Using $QUASAR^{TM}$ Phantom(Modus Medical Devices) and $GAFCHROMIC^{TM}$ EBT3 Film(Ashland, USA), verification carried out 4-D dose distribution for 4-D gamma pass rate. Result : The movement of the Inspiration and expiration phase was the most significant in axial direction of right lung, as $0.989{\pm}0.34cm$, and was the least significant in lateral direction of spinal cord, as -0.001 cm. The volume of right lung showed the greatest rate of change as 33.5 %. The maximal and minimal difference in PTV Conformity Index and Homogeneity Index between 3-dimensional dose evaluation and 4-dimensional dose evaluation, was 0.076, 0.021 and 0.011, 0.0 respectfully. The difference of 0.0045~2.76 % was determined in normal structures, using 4-D dose evaluation. 4-D gamma pass rate of every patients passed reference of 95 % gamma pass rate. Conclusion : PTV Conformity Index was more significant in all patients using 4-D dose evaluation, but no significant difference was observed between two dose evaluations for Homogeneity Index. 4-D dose distribution was shown more homogeneous dose compared to 3D dose distribution, by considering the movement from breathing which helps to fill out the PTV margin area. There was difference of 0.004~2.76 % in 4D evaluation of normal structure, and there was significant difference between two evaluation methods in all normal structures, except spinal cord. This study shows that normal structures could be underestimated by 3-D dose evaluation. Therefore, 4-D dose evaluation with Deformable Image Registration will be considered when the dose change is expected in normal structures due to patient's breathing pattern. 4-D dose evaluation with Deformable Image Registration is considered to be a more realistic dose evaluation method by reflecting the movement of normal structures from patient's breathing pattern.

• Progress in Medical Physics
• /
• v.21 no.2
• /
• pp.174-182
• /
• 2010

In this study, we evaluated feasibility of applying MTV (Metabolic Target Volume) to respiratory gated radiotherapy for more accurate treatment using various SUV (Standard Uptake Value) from PET images. We compared VOI (Volume of Interest) images from 50%, 30% and 5% SUV (standard uptake volume) from PET scan of an artificial target with GTV (Gross Tumor Volume) images defined by percentage of respiratory phase from 4D-CT scan for respiratory gated radiotherapy. It is found that the difference of VOI of 30% SUV is reduced noticeably comparing with that of 50% SUV in longitudinal direction with respect to total GTV of 4D-CT image. Difference of VOI of 30% SUV from 4D-PET image defined by respiratory phase from 25% inhalation to 25% exhalation, and GTV from 4D-CT with the same phase is shown below 0.6 cm in maximum. Thus, it is better to use 4D-PET images than conventional PET images for applying MTV to gated RT. From the result that VOI of 5% SUV from 4D-PET agrees well with reference image of 4D-CT in all direction, and the recommendation from department of nuclear medicine that 30% SUV be advised for defining tumor range, it is found that using less than 30%SUV will be more accurate and practical to apply MTV for respiratory gated radiotherapy.