• 대한금속재료학회지
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• 제49권2호
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• pp.161-166
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• 2011

The aim of this study was to determine the effect of high-energy mechanical milling (HEMM) time and sintering temperature on microstructure and mechanical properties of the TiAl composite fabricated by pulse current activated sintering. TiAl intermetallic powders were milled by HEMM for 1h, 4h, and 8h respectively. Thermal analysis was used to observe the phase transformation of the milled TiAl powders. The sintering time decreased with increase of milling time. The hardness and fracture toughness of the sintered specimens also was improved with increasing milling time. The grain size of the sintered specimens which was milled for 4h was in the range of 50~100 nm.

• 대한금속재료학회지
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• 제48권4호
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• pp.369-375
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• 2010

Ti-6Al-4V ELI alloy, which is commonly used as a biomaterial, is associated with a high elastic modulus and poor biocompatibility. This alloy presents a variety of problems on several areas. Therefore, the development of good non-toxic biocompatible biomaterials with a low elastic modulus is necessary. Particularly, hydroxyapatite (HA) is an attractive material for human tissue implantation. This material is widely used as artificial bone due to its good biocompatibility and similar composition to human bone. Many scientists have studied the fabrication of HA as a biomaterial. However, applications of bulk HA compact are hindered by the low strength of HA when it is sintered. Therefore, HA has been coated on Ti or Ti alloy to facilitate good bonding between tissue and the HA surface. However, there are many problems when doing this, such as the low bonding strength between HA and Ti due to the different thermal expansion coefficients and mechanical properties. In this study, a Ti-HA composite with a porous surface was successfully fabricated by pulse current activated sintering (PCAS) and a subsequent leaching process.

• 대한금속재료학회지
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• 제47권8호
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• pp.508-515
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• 2009

Ti-6Al-4V biomaterial is widely used as a bone alternative. However, Ti-6Al-4V ELI alloy suffers from numerous problems such as a high elastic modulus and high toxicity. Therefore, non-toxic biomaterials with low elastic moduli need to be developed. Ti-HA(hydroxyapatite) composites were fabricated in the present work by pulsed current activated sintering (PCAS) at $1000^{\circ}C$ under 60 MPa using mixed Ti and HA powders. The effects of HA content on the physical and mechanical properties of the sintered Ti-HA composites have been investigated. X-ray diffraction(XRD) analysis of the Ti-HA composites, including Ti-40 wt%HA in particular, revealed new phases, $Ti_{2}O$, CaO, $CaTiO_3$, and TixPy, formed by chemical reactions between Ti and HA during sintering. The hardness of the Ti-HA composites decreased with an increase in HA content. The corrosion resistance of these composites was observed to be an excellent candidate as a commercial Ti-6Al-4 V ELI alloy. A Ti-5 wt%HA composite fabricated by PCAS is recommended as a new biomaterial, because it offers good corrosion resistance, compressive strength, wear resistance, and biocompatibility, and a low Young's modulus.

• 대한금속재료학회지
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• 제46권4호
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• pp.223-226
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• 2008

The comparison of sintering behavior and mechanical properties of ultra-fine WC-10wt.%Co and WC-10wt.%Fe hard materials produced by high-frequency induction heated sintering (HFIHS) was accomplished using ultra fine powder of WC and binders(Co, Fe). The advantage of this process allows very quick densification to near theoretical density and prohibition of grain growth in nano-structured materials. Highly dense WC-10Co and WC-10Fe with a relative density of up to 99% could be obtained with simultaneous application of 60 MPa pressure and induced current within 1 minute without significant change in grain size. The hardness and fracture toughness of the dense WC-10Co and WC-10Fe composites produced by HFIHS were investigated.

• 대한방사선기술학회지:방사선기술과학
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• 제43권6호
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• pp.443-451
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• 2020

This study is to evaluate absorbed dose from right lung for brachytherapy and to estimate the effects of tissue heterogeneities on dose distribution for Iridium-192 source using Monte Carlo simulation. The study employed Geant4 code as Monte Carlo simulation to calculate the dosimetry parameters. The dose distribution of Iridium-192 source in solid water equivalent phantom including aluminium plate or steel plate inserted was calculated and compared with the measured dose by the ion chamber at various distances. And the simulation was used to evaluate the dose of gamma radiation absorbed in the lung organ and other organs around it. The dose distribution embedded in right lung was calculated due to the presence of heart, thymus, spine, stomach as well as left lung. The geometry of the human body was made up of adult male MIRD type of the computational human phantom. The dosimetric characteristics obtained for aluminium plate inserted were in good agreement with experimental results within 4%. The simulation results of steel plate inserted agreed well with a maximum difference 2.75%. Target organ considered to receive a dose of 100%, the surrounding organs were left the left lung of 3.93%, heart of 10.04%, thymus of 11.19%, spine of 12.64% and stomach of 0.95%. When the statistical error is performed for the computational human phantom, the statistical error of value is under 1%.

• 한국유기농업학회지
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• 제29권1호
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• pp.125-136
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• 2021

본 연구에서는 meta-analysis를 통해 TJP의 발현량과 육계의 생산성 간의 상관관계를 살펴보았다. TJP의 발현량은 생산성의 향상과 밀접한 관계가 있는 것으로 나타났으며, 특히 occludin의 발현이 육계의 생산성과 가장 큰 상관관계를 보이는 것으로 나타났다. Occludin 발현량 조절과 장 점막 건강이 육계 생산성 향상을 위한 영양 관리 전략 지표로 활용될 수 있을 것이다.

• 대한불안의학회지
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• 제18권2호
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• pp.92-100
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• 2022

Objective : The purpose of this study was to investigate the association among the fear of COVID-19, depression, risk perception, health belief, and preventive health behaviors related to COVID-19 among university students in Jeonbuk region. Methods : A cross-sectional study was conducted using an online questionnaire survey. The questionnaire included The Korean Version of Fear of COVID-19 Scale, the Korean Version of the Patient Health Questionnaire-9, and measurement tools adapted from previous studies for risk perception, health belief, and preventive health behaviors of subjects. We analyzed data using Pearson's correlation analysis, confirmatory factor analysis, and path analysis using SPSS 22 and AMOS 21. Results : The fear of COVID-19 showed significant positive influence on health belief as well as risk perception. Depression had a significant negative impact on preventive health behaviors and risk perception. Health belief showed a significant positive impact on preventive health behavior. Conclusion : Rresults revealed that the higher the level of depression was, the lower risk perception and performance of preventive health behavior were among university students in Jeonbuk region. As the level of the fear of COVID-19 became higher, the level of health belief and risk perception became higher. The higher the level of health belief was, the higher the performance level of preventive health were. Thus, it is prudent to increase the level of health belief, and lower the level of depression, in promoting preventive health behavior.

• 한국분말재료학회지
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• 제30권6호
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• pp.484-492
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• 2023

In this study, Ni-Y₂O₃ powder was prepared by alloying recomposition oxidation sintering (AROS), solution combustion synthesis (SCS), and conventional mechanical alloying (MA). The microstructure and mechanical properties of the alloys were investigated by spark plasma sintering (SPS). Among the Ni-Y₂O₃ powders synthesized by the three methods, the AROS powder had approximately 5 nm of Y₂O₃ crystals uniformly distributed within the Ni particles, whereas the SCS powder contained a mixture of Ni and Y₂O₃ nanoparticles, and the MA powder formed small Y₂O₃ crystals on the surface of large Ni particles by milling the mixture of Ni and Y₂O₃. The average grain size of Y₂O₃ in the sintered alloys was approximately 15 nm, with the AROS sinter having the smallest, followed by the SCS sinter at 18 nm, and the MA sinter at 22 nm. The yield strength (YS) of the SCS- and MA-sintered alloys were 1511 and 1688 MPa, respectively, which are lower than the YS value of 1697 MPa for the AROS-sintered alloys. The AROS alloy exhibited improved strength compared to the alloys fabricated by SCS and conventional MA methods, primarily because of the increased strengthening from the finer Y₂O₃ particles and Ni grains.

• 대한간호학회지
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• 제54권1호
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• pp.18-31
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• 2024

Purpose: This study aimed to investigate the impact of anthropometric indices of obesity (body mass index [BMI], waist circumference, waist hip ratio, and body fat percentage) on the incidence of hypertension in adults with prehypertension. Methods: A longitudinal study design using secondary data form the Korean Genome and Epidemiology Study was employed. The study included 1,838 adults with prehypertension tracked every two years from 2001 to 2018. Statistical analyses, including frequency assessments, number of cases per 1,000 person-years, log-rank tests, Kaplan-Meier curves, and Cox's proportional hazards regression, were conducted using SPSS version 25. Results: Over the observation period (15,783.6 person-years), 1,136 individuals developed hypertension. The incidence of hypertension was significantly higher in the obesity groups defined by BMI (hazard ratio [HR] = 1.33), waist circumference (HR = 1.34), waist hip ratio (HR = 1.29), and body fat percentage (HR = 1.31) compared to the non-obese group. These findings indicate an increased risk of hypertension associated with obesity as measured by these indices. Conclusion: The study underscores the importance of avoiding obesity to prevent hypertension in individuals with prehypertension. Specifically, BMI, waist circumference, waist hip circumference, and body fat percentage were identified as significant risk factors for hypertension. The results suggest the need for individualized weight control interventions, emphasizing the role of health professionals in addressing the heightened hypertension risk in this population.

• 구강회복응용과학지
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• 제39권4호
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• pp.204-213
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• 2023

구강 악안면 영역에서 외상으로 인해 발생한 골절에 대한 치료로 관혈적 혹은 비관혈적인 골절의 정복을 시행할 수 있다. 그러나, 최적의 정복이 이루어지지 않았거나 부정 유합이 발생할 경우, 하악골과 중안모 간의 구조적 관계가 상실되어 부정교합이 일어날 수 있다. 이러한 부정교합은 외상 후 부정교합이라 정의되며 안정적인 턱관절 위치의 확보 후 악교정 수술, 교정치료, 교합 재형성 및 보철적 재건 등이 외상 후 부정교합의 치료방법으로 제시되고 있다. 안정적인 턱관절은 교합 회복 전 부정교합의 재발 및 교합 변화를 방지하기 위해 필수적이며, 중심위 및 적응된 중심위는 가장 안정적인 턱관절의 위치로 교합 회복의 시작점이다. 본 증례는 다발성 안면 골절의 정복 후, 외상 후 부정교합이 발생하여 전악 교합의 회복을 위해 중심위에서 선택적 교합 조정 및 임플란트 지지 고정성 보철물로 보철적 재건을 시행한 증례로 교합 기능적으로 양호한 결과를 얻었기에 이를 보고하고자 한다.