• Nuclear Engineering and Technology
• /
• 제41권1호
• /
• pp.11-20
• /
• 2009

Radiation effects on materials are inherently multiscale phenomena in view of the fact that various processes spanning a broad range of time and length scales are involved. A multiscale modeling approach to embrittlement of pressure vessel steels is presented here. The approach includes an investigation of the mechanisms of defect accumulation, microstructure evolution and the corresponding effects on mechanical properties. An understanding of these phenomena is required to predict the behavior of structural materials under irradiation. We used molecular dynamics (MD) simulations at an atomic scale to study the evolution of high-energy displacement cascade reactions. The MD simulations yield quantitative information on primary damage. Using a database of displacement cascades generated by the MD simulations, we can estimate the accumulation of defects over diffusional length and time scales by applying kinetic Monte Carlo simulations. The evolution of the local microstructure under irradiation is responsible for changes in the physical and mechanical properties of materials. Mechanical property changes in irradiated materials are modeled by dislocation dynamics simulations, which simulate a collective motion of dislocations that interact with the defects. In this paper, we present a multi scale modeling methodology that describes reactor pressure vessel embrittlement in a light water reactor environment.

• Radiation Oncology Journal
• /
• 제2권2호
• /
• pp.221-228
• /
• 1984

The recogition that the vast majority of patients with small cell lung cancer have distant metastatic disease at the time of diagnosis lead to the use of systemic chemotherapy and consequent major improvement in survival, but recently evaulated treatment strategies, integration of large field chest irradiation with chemotherapy lead to the improved the local control and relapse free survival in limited SCLC. Therefore, it is logical to combine the two modalities in an effort to maximize the therapeutic effect. Authors performed the combination chemotherapy of CAV (Cyclophosphamide, Adriamycin, an6 Vincristine) and radiotherapy of primary tumor and regional lymphatics with prophylatic cranial irradiation in 42 patients of limited SCLC, from Mar. 1978 to Dec. 1982 Seoul National University Hospital. The results are as follows : 1. CR and PR after 2 cycles chemotherapy is $7\%$ and $43\%$, respectively however, subsequent response to radiotherapy is $38\%$ and $43\%$ in CR and PR. 2. Overall median survival peroid is 8.6 months. 3. 1 year and 2 years survival rate is $46.3\%$ and $20.5\%$, respectively. 4. Incidence of proven brain metastasis is $5\%$.

• 대한의용생체공학회:학술대회논문집
• /
• 대한의용생체공학회 1997년도 추계학술대회
• /
• pp.164-167
• /
• 1997

The treatment setup of patients during irradiation is an important aspect in relation to the success of radiotherapy. Imaging with the treatment beam is a widely used method or verification of the radiation field position relative to the target area, prior to or during irradiation. In this paper, Real time digital radiography system was implemented or verification of local error between simulation plan and radiation therapy machine. Portal image can be acquired by CCD camera, image board and pentium PC after therapy Radiation was converted into light by a metal/fluorescent Screen. The resulting image quality is comparable to film, so the imaging system represents a promising alternative to film as a method of verifying patient positioning in radiotherapy. Edge detection and field size measurement were also implemented and detected automatically for verification of treatment position. Field edge was added to the original image or checking the anatomical treatment verification by therapy technicians. By means of therapy efficiency improvement and decrease of Radiation side effects with these techniques, Exact Radiation treatments are expected.

• Nuclear Engineering and Technology
• /
• 제48권2호
• /
• pp.330-338
• /
• 2016

The U-Zr or U-TRU-Zr cylindrical metallic fuel slug used in fast reactors is known to swell significantly and to grow during irradiation. In neutronics simulations of metallic-fueled fast reactors, it is assumed that the slug has swollen and contacted cladding, and the bonding sodium has been removed from the fuel region. In this research, a realistic burnup-dependent fuel-swelling simulation was performed using Monte Carlo code McCARD for a single-batch compact sodium-cooled breed-and-burn reactor by considering the fuel-swelling behavior reported from the irradiation test results in EBR-II. The impacts of the realistic burnup-dependent fuel swelling are identified in terms of the reactor neutronics performance, such as core lifetime, conversion ratio, axial power distribution, and local burnup distributions. It was found that axial fuel growth significantly deteriorated the neutron economy of a breed-and-burn reactor and consequently impaired its neutronics performance. The bonding sodium also impaired neutron economy, because it stayed longer in the blanket region until the fuel slug reached 2% burnup.

• Journal of Welding and Joining
• /
• 제20권1호
• /
• pp.34-40
• /
• 2002

The laser strengthening of $35kgf/\textrm{mm}^2$ grade steel sheet is investigated by using $CO_2$ laser beam irradiation. The increase of tensile strength is dominated by the number of fully penetrated melting lines. Also, the optimal laser irradiation pattern is obtained by 3-point bending test. Local laser strengthening clay be effective for the weight reduction of automobile components where the tailored welded blank can not be applied.

• 대한기계학회논문집B
• /
• 제23권11호
• /
• pp.1379-1389
• /
• 1999

A new technique for control of size and shape of flame-made particles is Introduced. The characteristic sintering time can be controlled Independently of collision time by heating the particles with irradiation of laser because the sintering time strongly depends on temperature. A coflow oxy-hydrogen diffusion flame burner was used for $SiCl_4$ conversion to silica particle. Nanometer sized aggregates irradiated by a high power CW $CO_2$ laser beam were rapidly heated up to high temperatures and then were sintered to approach volume-equivalent spheres. The sphere collides much slower than the aggregate, which results in reduction of sizes of particles maintaining spherical shape. Light scattering of Ar ion laser and TEM observation using a local sampling device were used to confirm the above effects. When the $CO_2$ laser was irradiated at low position from the burner surface, particle generation due to gas absorption of laser beam occurred and thus scattering intensity increased with $CO_2$ laser power. At high irradiation position, scattering intensity decreased with $CO_2$ laser power and TEM image showed a clear mark of evaporation and recondensation of particles for high $CO_2$ laser power. When the laser was irradiated between the above two positions where small aggregates exist, average size of spherical particles obviously decreased to 58% of those without $CO_2$ laser irradiation with the spherical shape. Even for increased carrier gas flow rate by a factor of three, TEM photograph also revealed considerable reduction of particle size.

• Journal of Periodontal and Implant Science
• /
• 제40권6호
• /
• pp.276-282
• /
• 2010

Purpose: The present study was performed to evaluate the effect of erbium:yttrium-aluminium-garnet (Er:YAG) laser irradiation on the change of hydroxyapatite (HA)-coated implant surface microstructure according to the laser energy and the application time. Methods: The implant surface was irradiated by Er:YAG laser under combination condition using the laser energy of 100 mJ/pulse, 140 mJ/pulse and 180 mJ/pulse and application time of 1 minute, 1.5 minutes and 2 minutes. The specimens were examined by surface roughness evaluation and scanning electron microscopic observation. Results: In scanning electron microscope, HA-coated implant surface was not altered by Er:YAG laser irradiation under experimental condition on 100 mJ/pulse, 1 minute. Local areas with surface melting and cracks were founded on 100 mJ/pulse, 1.5 minutes and 2 minutes. One hundred forty mJ/pulse and 180 mJ/pulse group had surface melting and peeling area of HA particles, which condition was more severe depending on the increase of application time. Under all experimental condition, the difference of surface roughness value on implant surface was not statistically significant. Conclusions: Er:YAG laser on HA-coated implant surface is recommended to be irradiated below 100 mJ/pulse, 1 minute for detoxification of implant surface without surface alteration.

• 한국육종학회지
• /
• 제42권4호
• /
• pp.365-373
• /
• 2010

TILLING (Targeting Induced Local Lesions IN Genomes) is broadly regarded as an excellent methodology for reverse genetics applications. Approximately 15,000 $M_3$ TILLING lines have been developed via the application of gamma-ray irradiation to rice seeds (cv. Donganbyeo), followed by subsequent selections. In an effort to evaluate the genetic diversity of the TILLING population, we have employed the AFLP multiple dominant marker technique. A total of 96 (0.64%) TILLING lines as well as Donganbyeo were selected randomly and their genetic diversity was assessed based on AFLP marker polymorphisms using 5 primer combinations. An average of 100.4 loci in a range of 97 to 106 was detected using these primer combinations, yielding a total of 158 (31.4%) polymorphic loci between Donganbyeo and each of the 96 lines. A broad range of similarity from 80% to 96% with an average of 89.4% between Donganbyeo and each of the 96 lines was also observed, reflecting the genetic diversity of the TILLING population. Approximately 28 polymorphic loci have been cloned and their sequences were BLAST-searched against rice whole genome sequences, resulting in 20 matches to each of the gene bodies including exon, intron, 1 kb upstream and 1 kb downstream regions. Six polymorphic loci evidenced changes in the coding regions of genes as compared to the rice pseudomolecules, 4 loci of which exhibited missense mutations and 2 loci of which exhibited silent mutations. Therefore, the results of our study show that the TILLING rice population should prove to be a useful genetic material pool for functional genomics as well as mutation breeding applications.

• Asian Pacific Journal of Cancer Prevention
• /
• 제14권12호
• /
• pp.7569-7576
• /
• 2013

Background: The purpose of this article is to present preliminary results of simultaneous boost irradiation radiotherapy for locally advanced nasopharyngeal carcinoma (NPC). Methods: Fifty-eight patients who underwent simultaneous boost irradiation radiotherapy for NPC in Cancer Center of Sun Yat-sen University between September 2004 and December 2009 were eligible. Acute and late toxicities were scored weekly according to the Radiation Therapy Oncology Group (RTOG) acute and late radiation morbidity scoring schemes. An especial focus was on evidence of post-radiation brain injury. Also quality of life was analysed according to the EORTC (European Organisation for Research and Treatment of Cancer) recommendations. Discrete variables were compared by ${\chi}^2$ test. The Kaplan-Meier method was used to calculate the survival rates and generate survival curves. Results: A total of 58 patients with a mean follow-up time of 36 months completed clinical trials.Fifty-seven patients (98.3) achieved complete remission in the primary sites and cervical lymph nodes, with only one patient (1.7%) showing partial remission.The most frequently observed acute toxicities during the concurrent chemoradiotherapy were mucositis and leucopenia. Four patients (6.9%) had RTOG grade 3 mucositis, whereas four patients (6.9%) had grade 3 leucopenia. No patient had grade 4 acute toxicity. Three (5.17%) of the patients exhibited injury to the brain on routine MRI examination, with a median observation of 32 months (range, 25-42months). All of them were RTOG grade 0. The 3-year overall, regional-free and distant metastasis-free survival rates were 85%, 94% and 91%, respectively. Conclusion: Simultaneous boost irradiation radiotherapy is feasible in patients with locally advanced nasopharyngeal carcinoma. The results showed excellent local control and overall survival, with no significant increase the incidence of radiation brain injury or the extent of damage. A larger population of patients and a longer follow-up period are needed to evaluate ultimate tumor control and late toxicity.

• Radiation Oncology Journal
• /
• 제9권1호
• /
• pp.87-91
• /
• 1991

영남대학병원에서는 1988년 6월 15일부터 1990년 9월 15일까지 절제가능한 국소 진행된 위암 환자중 원격 전이를 추인할 수 없었던 환자 총 28명을 prospective randomized protocol에 의한 치료를 계획하였다. 28명중, 개복후 절제가 불가능했던 환자 3명과 stage la로 판명된 환자 1명을 제외 한 24명에서 외과적 근치절제수술후 1500cGy를 giuev의 전자선을 이용하여 1회에 조사하였다. 외부 방사선 치료는 수술후 4주 이내에 시작하여 하루 180 cGy 주 5회 치료법으로 $4300\sim4500$ cGy를 조사하였다. 항암요법은 protoco떼 의하여 5-FU, Mitomycin-C, Adriamycin, Uraful을 여러 가지 조합으로 투여하였다. 3개월에서 31개월 간의 추적기간 중에 방사선 조사와 관계되는 심한 부작용은 보고되지 않았다. 짧은 추적 기간이므로 생존율을 산출할 수 없겠으나 수술중 방사선치료, 외부방사선 치료와 여러가지 항암제를 병합 투여하였음에도 불구하고 심한 부작용이 발견되지 않았을 뿐 아니라 현재까지 국소재발이 한 예에서도 발견되지 않았음으로 수술중 방사선 치료의 국소 재발의 억제 및 방지의 효과가 확실시되며 계속되는 추적 검사에서도 좋은 생존율이 기대된다.