• Title/Summary/Keyword: Helical mode

Search Result 64, Processing Time 0.034 seconds

Four-Dimensional Computed Tomography for Gated Radiotherapy: Retrospective Image Sorting and Evaluation

  • Lim, Sang-Wook;Park, Sung-Ho;Back, Geum-Mun;Ahn, Seung-Do;Shin, Seong-Soo;Lee, Sang-Wook;Kim, Jong-Hoon;Choi, Eun-Kyuong;Kwon, Soo-Il
    • Proceedings of the Korean Society of Medical Physics Conference
    • /
    • 2005.04a
    • /
    • pp.71-74
    • /
    • 2005
  • To introduce the four-dimensional computed tomography (4DCT, Light Speed RT, General Electric, USA) scanner newly installed in our department and evaluate its feasibility for gated radiotherapy. Respiratory signal measured by real-time position management (RPM$^{\circledR}$, Varian Medical, USA) was recorded in synchronization with the 4DCT scanner. 4DCT data were acquired in axial cine mode and sorted retrospective image based on respiratory phase. PTVs delineated from helical CT and 4DCT images were compared. The PTV delineated from conventional helical CT images was 2 cc larger than that from 4DCT images. Dose in PTV of the plan from retrospective CT was 99.3% (minimum=72.0%, maximum=106.5%) and that of helical CT plan was 95.2% (minimum=24.1%, maximum=106.4%) of prescribed dose. Comparing with DVHs of both plan, the coverage for 4CDT plan was 3.7% improved. It is expected that 4DCT could improve tumor control and reduce radiation toxicity for liver cancer.

  • PDF

Analysis of Higher Order Structure of 5S rRNA from Pseudomonas alcaligenes by using Pb(Ⅱ) Ion (Pb(Ⅱ) 이온을 이용한 Pseudomonas alcaligenes 5S rRNA의 고차원 구조 분석)

  • Kim, Sangbumn;Lee, Younghoon;Park, Inwon
    • Journal of the Korean Chemical Society
    • /
    • v.39 no.6
    • /
    • pp.453-458
    • /
    • 1995
  • We have applied Pb2+ to the structural analysis of 5S rRNA from Pseudomonas alcaligenes. The mode of Pb2+-induced clevage on 5S rRNA has shown several specific features which may be utilized for the examination of tertiary structure of 5S rRNA: Pb2+ does not attack the stable helical stems; single stranded regions or bulges are attacked in variable susceptibilities depending on the positions of the sequences or the bases on the molecule; unstable helical region d is not attacked at all; only 3' sided strand of unstable helical stem C is weakly attacked, leaving 5' sided strand unattacked. Based on the Pb2+ cleavage properties and the structural analysis of Xanthomonas celebensis 5S rRNA, we have proposed a working hypothesis for the tertiary interactions in 5S rRNA.

  • PDF

A Study on Photoresist Stripping Using High Density Oxygen Plasma (고밀도 산소 플라즈마를 이용한 감광제 제거공정에 관한 연구)

  • Jung, Hyoung-Sup;Lee, Jong-Geun;Park, Se-Geun;Yang, Jae-Kyun
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
    • /
    • v.11 no.2
    • /
    • pp.95-100
    • /
    • 1998
  • A helical inductively coupled plasma asher, which produces low energy and high density plasma, has been built and investigated for photoresist stripping process. Oxygen ion density in the order of $10^{11}/cm^3$ is measured by Langmuir probe, and higher oxygen radical density is observed by Optical Emission Spectrometer. As RF source power is increased, the plasma density and thus photoresist stripping rate are increased. Independent RF bias power to the wafer stage provides a dc bias to the wafer and an ability to add the ion assisted reaction. At 1 KW of the source power, the coupling mechanism of the RF power to the plasma is changed from the inductive mode to the capacitive one at about 1 Torr. This change causes the plasma density and ashing rate decreases abruptly. The critical pressure of the mode change becomes larger with larger RF power.

  • PDF

The Critical Speed Analysis of Gear Train for Hydro-Mechanical Continuously Variable Transmission (기계유압식 무단변속기용 기어트레인에 대한 위험속도 해석)

  • Bae, Myung Ho;Bae, Tae Yeol;Choi, Sung Kwang
    • Journal of Drive and Control
    • /
    • v.14 no.4
    • /
    • pp.71-78
    • /
    • 2017
  • The power train of hydro-mechanical continuously variable transmission (HMCVT) for 8-ton class forklift includes hydro-static units, hydraulic multi-wet disc brake & clutches and complex helical & planetary gears. The helical & planetary gears are key components of HMCVT's power train wherein strength problems are the main concerns including gear bending stress, gear compressive stress, and scoring failure. Many failures in power train gears of HMCVT are due to the insufficient gear strength and resonance problems caused by major excitation forces, such as gear transmission error of mating gear fair in the transmission. In this study, wherein excitation frequencies are the gear tooth passing frequencies of the mating gears, a Campbell diagram is used to calculate the power train gears' critical speeds. Mode shapes and natural frequencies of the power train gears are calculated by CATIA V5. These are used to predict resonance failures by comparing the actual working speed range with the critical speeds due to the gear transmission errors of HMCVT's power train gears.

Doses of Coronary Study in 64 Channel Multi-Detector Computed Tomography : Reduced Radiation Dose According to Varity of Examnination Protocols (64 채널 Multi-Detector Computed Tomography를 이용한 관상동맥검사의 선량 : 검사 프로토콜 다변화에 따른 환자선량 감소)

  • Kim, Moon-Chan
    • Journal of radiological science and technology
    • /
    • v.32 no.3
    • /
    • pp.299-306
    • /
    • 2009
  • Purpose : To compare radiation dose for coronary CT angiography (CTA) obtained with 6 examination protocols such as a retrospectively ECG gated helical scan, a prospectively ECG gated sequential scan, low kVp technique, and cardiac dose modulation technique. Materials and Methods : Coronary CTA was performed by using 6 current clinical protocols to evaluate effective dose and organ dose in primary beam area with anthropomorphic female phantom and glass dosimetric system in 64 channel multi-detector CT. After acquiring topograms of frontal and lateral projection with 80 kVp and 10 mA, main coronary scan was done with 0.35 sec tube rotation time, 40 mm collimation ($0.625\;mm{\times}64\;ea$), small scan field of view (32 cm diameter), 105 mm scan length. Heart beat rate of phantom was maintained 60 bpm in ECG gating. In constant mAs technique 120 kVp, 600 mA was used, and 100 kVp for low kVp technique. In a retrospectively ECG gated helical CT technique 0.22 pitch was used, peak mA (600 mA) was adopted in range of $40{\sim}80%$ of R-R interval and 120mA(80% reduction) in others with cardiac dose modulation. And 210 mAs was used without cardiac dose modulation. In a prospectively ECG gated sequential CT technique data were acquired at 75% R-R interval (middle diastolic phase in cardiac cycle), and 120 msec additional padding of the tube-on time was used. For effective dose calculation region specific conversion factor of dose length product in thorax was used, which was recommended by EUR 16262. Results : The mean effective dose for conventional coronary CTA without cardiac dose modulation in a retrospectively ECG gated helical scan was 17.8 mSv, and mean organ dose of heart was 103.8 mGy. With low kVp and cardiac dose modulation the mean effective dose showed 54.5% reduction, and heart dose showed 52.3% reduction, compared with that of conventional coronary CTA. And at the sequential scan(SnapShot pulse mode) under prospective ECG gating the mean effective dose was 4.9 mSv, this represents an 72.5% reduction compared with that of conventional coronary CTA. And heart dose was 33.8 mGy, this represents 67.4% reduction. In the sequential scan technique under prospective ECG gating with low kVp the mean effective dose was 3.0 mSv, this represents an 83.2% reduction compared with that of conventional coronary CTA. And heart dose was 17.7 mGy, this represents an 82.9% reduction. Conclusion : In coronary CTA at retrospectively ECG gated helical scan, cardiac dose modulation technique using low kVp reduced dose to 50% above compared with the conventional helical scan. And the prospectively ECG gated sequential scan offers substantially reduced dose compared with the traditional retrospectively ECG gated helical scan.

  • PDF

Design of Tx.Rx broadband antenna on LTCC at K/Ka band (LTCC 공정을 이용한 K/Ka 대역 송수신 겸용 이중 급전 안테나)

  • Cheon, Young-Min;Kim, Sung-Nam;Oh, Min-Seok;Choi, Jae-Ick;Pyo, Cheol-Sig;Lee, Jong-Moon;Cheon, Chang-Yul
    • Proceedings of the KIEE Conference
    • /
    • 2004.07c
    • /
    • pp.2055-2057
    • /
    • 2004
  • The Ku band that has been using for the satellite communication and broadcasting would be changed to K/Ka bands. The satellite system requires the antenna structure to fabricate low loss and small antenna that is able to be integrated with other Rf circuits for both Rx and Tx. So we should design it with dual feed antennas at K/Ka bands, high isolation between two different feeds and broadband circular polarization. This paper proposes the LTCC(Low Temperature Co-fired Ceramic) process for integration with other Rf circuits and the Axial mode of the helical antenna to satisfy those requirements.

  • PDF

Active Control of Impinging Jets Using Bifurcating Excitations (분기 가진을 통한 충돌제트 능동 제어 연구)

  • Kim, Jungwoo
    • Journal of the Korean Society of Manufacturing Technology Engineers
    • /
    • v.22 no.3_1spc
    • /
    • pp.525-530
    • /
    • 2013
  • The objective of the present study is to investigate the heat transfer characteristics of turbulent impinging jets with bifurcating excitations. Bifurcating excitations use the dual mode, dual frequency forcing, where an axial forcing frequency is equal to double the helical forcing frequency. Under the bifurcating excitation, the heat transfer significantly increases in one plane (bifurcating plane), while nearly no heat transfer occurs in the perpendicular plane (bisecting plane). This result is closely associated with the change in the vortical structures caused by the excitation.

트로코이달 헬리컬 기어의 비정상상태 유한요소해석

  • ;;Yong Bok Park;Dong Yol Yang
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 1994.03a
    • /
    • pp.37-46
    • /
    • 1994
  • In metal forming, there ar problems with recurrent geometric characteristics and without explicitly prescribed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. The present study deals with nonsteady-state three-dimensional finite element analysis for extrusion of a trocoidal helical gear through a curved die. The boundary-directed remeshing scheme based on the modular remeshing technique is developed to reduce the errors arising in fitting old and new mesh systems. The computed extrusion pressure in reaching the near steady-state loading stage is compared with the results of the experiment and the steady-state analysis. The three-dimensional deformed pattern involving warping at the extruded end due to torsional deformation mode is demonstrated.

  • PDF

The Interaction of Mastoparan B from Venom of a Hornet Vespa Basalis with Phospholipid Matrices

  • 박남규;Yuhji Yamato;Sannamu Lee;Gohsuke Sugihara;박장수;강신원
    • Bulletin of the Korean Chemical Society
    • /
    • v.17 no.3
    • /
    • pp.239-244
    • /
    • 1996
  • Mastoparan B (MP-B) that is a novel MP isolated from the hornet Vespa basalis, was studied as compared with MP, in terms of interaction with phospholipid bilayer and antimicrobial activity. MP-B has more hydrophilic amino acid residues in hydrophilic face of amphiphilic α-helical structure than MP. The both peptides exhibited considerably different effect on interaction with lipid bilayers, e.g. their conformation in the presence of acidic and neutral liposomes, dye-release ability from encapsulated liposomes, but on the whole the interaction mode was similar. On antimicrobial activity, MP had a strong activity against Gram-positive bacteria but no against Gram negative ones. Contrary to this, MP-B had a strong activity against Gram-positive and potent against Gram-negative ones. Since both peptides have almost same residues on the hydrophobic side, such more hydrophilic surface on the molecule seems to lead to the subtle change in its interaction with membranes, resulting in the alternation in its biological activity.

Vibration characteristics of power differential gear train for 2.5MW wind turbine (2.5MW 풍력발전기 동력분기식 기어트레인의 진동특성)

  • Kim, Jung Su;Park, No Gill;Lee, Hyoung Woo
    • Journal of Advanced Marine Engineering and Technology
    • /
    • v.38 no.3
    • /
    • pp.253-261
    • /
    • 2014
  • In this paper, vibration analysis of power differential gear train for 2.5MW wind turbine system is analyzed. which system is composed of two planetary gear set, one helical gear set and main shaft that connected by flange. Planetary gear set, helical gear set, main shaft are modeled in MASTA program and housing, torque arm, carrier, flange components are modeling by finite element method. Each models are combined by component mode superposition. To analysis of natural vibration characteristic about 2.5MW wind turbine gear train was performed and check about critical speed with wind load, mass unbalance, angle misalignment excitation frequency.