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A Study of Co, Ni, Mn, and Al Containing Goethites by Mossbauer Spectroscopy
Eng Chan Kim,Hyeun Gook Hwang,Yong Soon Hwang,Jung Gi Kim,V. I. Nikolaev 한국자기학회 1997 Journal of Magnetics Vol.2 No.4
To determine whether there is an ionic substitution of Ni, Co, Mn, and Al for Fe in synthetic goethites these materials have been studied by Mossbauer spectroscopy at various temperatures ranging from 77 to 400 K. It is found that the presence of substituting elements in magnetically ordered structure of crystals may change the shape of Mossbauer spectra of these materials. The approximate distribution function of the effective magnetic field in the Fe nucleus p(Hn) is obtained from the Mossbauer spectra. It is noted that the mean value of p(Hn) and its integral width can be taken as a measure of substitution in goethites.
Eng-Chan Kim,Yeong-Cheol Heo,Jae-Hwan Cho,Hyun-Jeong Lee,Hae-Kag Lee 한국자기학회 2014 Journal of Magnetics Vol.19 No.2
In this study we evaluated that flow rate changes affect the (time of flight) TOF image and contrast-enhanced (CE) in a three-dimensional TOF angiography. We used a 3.0T MR System, a nonpulsatile flow rate model. Saline was used as a fluid injected at a flow rate of 11.4 cm/sec by auto injector. The fluid signal strength, phantom body signal strength and background signal strength were measured at 1, 5, 10, 15, 20 and 25-th cross-section in the experienced images and then they were used to determine signal-to-noise ratio and contrastto- noise ratio. The inlet, middle and outlet length were measured using coronal images obtained through the maximum intensity projection method. As a result, the length of inner cavity was 2.66 mm with no difference among the inlet, middle and outlet length. We also could know that the magnification rate is 49-55.6% in inlet part, 49-59% in middle part and 49-59% in outlet part, and so the image is generally larger than in the actual measurement. Signal-to-noise ratio and contrast-to-noise ratio were negatively correlated with the fluid velocity and so we could see that signal-to-noise ratio and contrast-to-noise ratio are reduced by faster fluid velocity. Signal-to-noise ratio was 42.2-52.5 in 5-25th section and contrast-to-noise ratio was from 34.0-46.1 also not different, but there was a difference in the 1st section. The smallest 3D TOF MRA measure was 2.51 ± 0.12 mm with a flow velocity of 40 cm/s. Consequently, 3D TOF MRA tests show that the faster fluid velocity decreases the signal-to-noise ratio and contrast-to-noise ratio, and basically it can be determined that 3D TOF MRA and 3D CE MRA are displayed larger than in the actual measurement.
A Study of Magnetic Properties in $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ by Magnetic Annelaing
Kim, Eng-Chan,Kim, Jin-Eui,Nam, Hyo-Duk The Korean Institute of Electrical and Electronic 2000 Transactions on Electrical and Electronic Material Vol.1 No.3
The crystallographic and high frequency characteristics of $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ soft magnetic alloys were investigated under magnetic field annealing, The crystallization fraction of annealed samples with longitudinal magnetic fields is higher than that of samples without magnetic field. When the transverse magnetic field is applied, the crystallization fraction does not increases but decreases until $500^{circ}C$. It is found that for samples, the saturation induction are all same with 1.3 T. The coercive field of as-cast samples is 1.03 A/cm, but in annealed samples it decrease from 0.56 to 0.1A/cm with increasing annealing temperature from 400 to $550^{circ}C$. The squareness of annealed samples under transverse magnetic field has a small value than that of both without field and with longitudinal field annealing. It is noted that the magnetic field annealing with transverse direction to amorphous $Fe_{73.9}Cu_{1.0}Nb_{3.5}Si_{14.0}B_{7.6}$ profoundly influenced on the Mossbauer spectra in contrast to that with longitudinal direction and without magnetic field.
스피넬 구조의 자유 매개 변수와 뫼스바우어 흡수선 이동
김응찬 嶺南大學校基礎科學硏究所 1999 基礎科學硏究 Vol.19 No.-
The dependence of the Mo¨ssbauer lineshift δ in oxygen ferrite-spinels on the free parameter of the structure u is considered. The mutual disposition of the lines for the A and B points in the spectrum depends significantly on the oxygen parameter u. Within the framework of the field theory of ligands, theoretical dependences are obtained for the difference in the shifts Δδ^RA ≡ δ^B-δ^A as a function of u, at various values of the lattice parameter a. This difference is expedient for comparison with experimental data, since it does not depend on the choice of radiation source and scarcely depends on a. The available experimental data for ferrite-spinels with Fe^3+ ions at points A and B agree with the results of the calculations. In particular, the trend of the difference Δδ^BA to sign reversal with rise in u is confirmed. According to the results of the calculations, sign reversal should be observed at u= u_cr=0.3845 for the case when a=8.30A˚.
반강자성 CuFeS2-xSex의 결정학적 및 자기적 성질
김응찬 嶺南大學校 基礎科學硏究所 1997 基礎科學硏究 Vol.17 No.-
CuFeS???Se has been studied by Mossbauer spectroscopy and x-ray diffraction. The crystal is found to have a tetragonal structure and the lattice constants a? and c? increase linearly with increasing selenium concentration. It is noteworthy that the replacement of S by Se in the chalcopyrite decreases the strength of both the superexchange interaction and the interatomic binding. Isomer shift indicates a ferric character for the iron ions. The Debye temperature is found to be decreased with increasing selenium concentration.
김응찬 嶺南大學校基礎科學硏究所 1999 基礎科學硏究 Vol.19 No.-
We used the discrepancy method to receive the quantitive information about the distribution function of the effective magnetic field H_n in Mo¨ssbauer spectroscopy. NiFe_2O_4 was used as a model object because of a priori known information about the desired function. To demonstrate discrepancy method ability in search for the distribution function of the effective magnetic field on nuclei we used data for the experimental spectrum of ^57Fe in NiFe_2O_4 a different parameters. An outstanding peculiarity of the discrepancy method, that if one intend to receive more detailed information about the distribution function the noise level will increase at a great extent, was manifested in the obtained results.
Nyanti Larry Ellee,Chua Chia Zhen,Loo Han Chuan,Khor Cheng Zhi,Toh Emilia Sheau Yuin,Gill Rasvinder Singh,Chan Eng Tat,Tan Ker Yin,Rosli Taufiq,Rahim Muhammad Aklil Abd,Ibrahim Arfian,Huan Nai Chien,R 대한결핵및호흡기학회 2023 Tuberculosis and Respiratory Diseases Vol.86 No.4
Background: Attitudes towards smoking, lung cancer screening, and perceived risk of lung cancer have not been widely studied in Malaysia. The primary objective of this study was to describe the factors affecting the willingness of high-risk current smokers and ex-smokers to undergo low-dose computed tomography (LDCT) screening for lung cancer.Methods: A prospective, cross-sectional questionnaire study was conducted in current smokers or ex-smokers aged between 55 and 80 years at three hospitals in Kota Kinabalu, Sabah, Malaysia. The questionnaire recorded the following parameters: perceived lung cancer risk; Prostate Lung Colon Ovarian Cancer 2012 risk prediction model excluding race and ethnicity predictor (PLCOm2012norace); demographic characteristics; psychosocial characteristics; and attitudes towards lung cancer and lung cancer screening.Results: A vast majority of the 95 respondents (94.7%) indicated their willingness to undergo screening. Stigma of lung cancer, low levels of knowledge about lung cancer symptoms, concerns about financial constraints, and a preference for traditional medication were still prevalent among the respondents, and they may represent potential barriers to lung cancer screening uptake. A desire to have an early diagnosis (odds ratio [OR], 11.33; 95% confidence interval [CI], 1.53 to 84.05; p=0.02), perceived time constraints (OR, 3.94; 95% CI, 1.32 to 11.73; p=0.01), and proximity of LDCT screening facilities (OR, 14.33; 95% CI, 1.84 to 111.4; p=0.01) had significantly higher odds of willingness to undergo screening.Conclusion: Although high-risk current smokers and ex-smokers are likely to undergo screening for lung cancer, several psychosocial barriers persist. The results of this study may guide the policymakers and clinicians regarding the need to improve lung cancer awareness in our population.
Jong Soo Han,Choong Jin Yang,Eon Byeung Park,Eng Chan Kim 한국자기학회 2005 Journal of Magnetics Vol.10 No.1
Precisely refined Mossbauer study and nano structure observation revealed that intergranular phase formed between α-Fe and Nd₂Fe₁₄B phase in NdFeNbB alloys plays a significant role on the magnetic properties. The intergranular interaction was characterized in term of Henkel Plot (δM plot), and hyperfine field, quardrupole splitting and isomer shift were refined to predict the presence and role of the intergranular phase. By the addition of Nb into Nd_8Fe_(86)B_6 composition, coercivity was found to increase by 25% due to the refinement of average grain size of both the soft and hard magnetic phases which was decreased from 50 ㎚ of virgin Nd_8Fe_(86)B_6 to 25 ㎚ in Nd_8Fe_(85)Nb₁B_6 alloys. The role of Nb addition was confirmed to stabilize the Nd₂Fe₁₄B lattice preventing from thermal vibration of the corresponding sites substituted Fe by Nb atoms in all sites in the Nd₂Fe₁₄B lattice. The enhanced coercivity was originated from the exchange hardening of soft and amorphous phases surrounding the hard magnetic Nd₂Fe₁₄B crystal.