• 한국식생활문화학회지
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• 제24권2호
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• pp.191-198
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• 2009

The objective of this study was to investigate the effects of different amounts of pumpkin powder on the quality characteristics of hobakpyeon using physicochemical and sensory properties, as well as on its retrogradation rate during storage. As the amount of pumpkin powder increased, the following effects on the quality characteristics were observed: moisture and amylose contents decreased while protein content increased (p<0.05), and in vitro protein digestibility (IVPD) decreased (p<0.05). Levels of slowly digestible starch and resistant starch fractions increased, while the content of rapidly digestible starch decreased. The starch digestion index and rapidly available glucose content also decreased. Among the physical properties, the L-value decreased while the b-value increased (p<0.05). Texture profile analysis revealed that all textural properties except adhesiveness decreased, and presented significant differences in hardness and chewiness (p<0.05). Sensory properties such as color, flavor, and sweetness increased while others such as wetness and chewiness decreased (p<0.05). Effects on the physicochemical properties during refrigerated storage were also compared between the control and 9% hobakpyeon (9%HP). According to the results, moisture content gradually decreased in the 9%HP compared to the control. Amylose content significantly increased in 9%HP whereas no significant changes were observed in the control. In both types of hobakpyeon, IVSD decreased significantly, showing higher values in 9%HP, whereas mechanical hardness increased, showing lower values in 9%HP. The L-value decreased significantly in the 9%HP whereas no significant changes were observed in the control. In conclusion, the above results suggest that hobakpyeon with low IVSD may be obtained by the addition of 9% pumpkin powder, and also showed that pumpkin powder delayed the rate of retrogradation in 9%HP during storage.

• 분석과학
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• 제22권4호
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• pp.302-306
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• 2009

철강 중의 미량 붕소는 소재의 기계적, 물리적 특성에 중요한 영향을 준다. 즉발감마선 방사화 분석법에 의해 저합금강 시료 중의 미량 붕소를 측정하였다. 시료는 한국표준과학연구원에서 제조한 저합금강 표준물질KRISS 101-01-C21~C26을 이용하였으며, 측정방법의 유효성 확인을 위해 NIST SRM 362, 364, 1761, 1762를 정확도관리용 시료로 사용하였다. NIST SRM 362를 제외하고는 측정 농도가 인증값의 불확도 범위내에서 잘 일치하였다. 불확도는 ISO guideline에 따라 평가하였으며, 포함인자 2를 적용하여 확장불확도를 산출하였다. 붕소 농도 mg/kg수준에서 상대확장불확도는 3%에서 7% 사이였다. 그 결과를 용매추출-유도결합플라스마 방출분광분석결과와 비교하여 제시하였다.

• 대한토목학회논문집
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• 제26권1D호
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• pp.73-79
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• 2006

본 연구의 목적은 포장의 설계수명과 공용년수를 증대시켜 아스팔트 포장의 유지보수비용을 감소시킬 수 있는 장수명 아스팔트 포장용 고강성 혼합물을 개발하는데 있다. 따라서 본 연구에서는 고강성 아스팔트 바인더를 개발하였으며 다양한 실내 물성시험을 수행하였다. 실내 물성시험 결과 새롭게 개발된 고강성 아스팔트 바인더가 프랑스의 고강성 아스팔트 바인더와 유사하다는 것을 알 수 있었고, 바인더 외에 혼합물의 공용성을 평가하기 위해 기존의 일반아스팔트 혼합물과 새롭게 개발된 고강성 아스팔트 혼합물의 비교 시험을 수행하였다. 공용성 시험 결과 동탄성계수 측정시험에서는 고강성 아스팔트 혼합물이 일반 아스팔트 혼합물보다 강성에 있어 $5^{\circ}C$에서는 10~15%, $15^{\circ}C$에서는 20~25%, $30^{\circ}C$에서는 거의 2배가 증가함을 알 수 있었다. 또한 수분손상시험 및 휠트래킹시험, 피로시험을 수행한 결과 일반 아스팔트 혼합물에 비해 고강성 아스팔트 혼합물의 공용성이 우수한 것으로 평가되었다.

• 한국재료학회지
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• 제33권7호
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• pp.285-294
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• 2023

Porous ceramics are used in various industrial applications based on their physical properties, including isolation, storage, and thermal barrier properties. However, traditional manufacturing environments require additional steps to control artificial pores and limit deformities, because they rely on limited molding methods. To overcome this drawback, many studies have recently focused on fabricating porous structures using additive manufacturing techniques. In particular, the binder jet technology enables high porosity and various types of designs, and avoids the limitations of existing manufacturing processes. In this study, we investigated process optimization for manufacturing porous ceramic filters using the binder jet technology. In binder jet technology, the flowability of the powder used as the base material is an important factor, as well as compatibility with the binder in the process and for the final print. Flow agents and secondary binders were used to optimize the flowability and compatibility of the powders. In addition, the effects of the amount of added glass frit, and changes in sintering temperature on the microstructure, porosity and mechanical properties of the final printed product were investigated.

• Restorative Dentistry and Endodontics
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• 제45권4호
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• pp.50.1-50.11
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• 2020

Objectives: In this study, we investigated the potential of amoxicillin-loaded polymeric microspheres to be delivered to tooth root infection sites via a bioactive reparative cement. Materials and Methods: Amoxicillin-loaded microspheres were synthesized by a spray-dray method and incorporated at 2.5% and 5% into a mineral trioxide aggregate cement clinically used to induce a mineralized barrier at the root tip of young permanent teeth with incomplete root development and necrotic pulp. The formulations were modified in liquid:powder ratios and in composition by the microspheres. The optimized formulations were evaluated in vitro for physical and mechanical eligibility. The morphology of microspheres was observed under scanning electron microscopy. Results: The optimized cement formulation containing microspheres at 5% exhibited a delayed-release response and maintained its fundamental functional properties. When mixed with amoxicillin-loaded microspheres, the setting times of both test materials significantly increased. The diametral tensile strength of cement containing microspheres at 5% was similar to control. However, phytic acid had no effect on this outcome (p > 0.05). When mixed with modified liquid:powder ratio, the setting time was significantly longer than that original liquid:powder ratio (p < 0.05). Conclusions: Lack of optimal concentrations of antibiotics at anatomical sites of the dental tissues is a hallmark of recurrent endodontic infections. Therefore, targeting the controlled release of broad-spectrum antibiotics may improve the therapeutic outcomes of current treatments. Overall, these results indicate that the carry of amoxicillin by microspheres could provide an alternative strategy for the local delivery of antibiotics for the management of tooth infections.

• Safety and Health at Work
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• 제14권3호
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• pp.325-331
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• 2023

Background: Heat stress is a harmful physical hazard in many occupational settings. However, consequences of occupational heat exposure among workers in a sugarcane factory in Ethiopia are not well characterized. This study aimed to assess the level of occupational heat exposure-related symptoms and contributing factors. Methods: In this cross-sectional study, five workstations were selected for temperature measurement. Heat stress levels were measured using a wet-bulb globe temperature index meter. A stratified random sampling technique was used to select 1,524 participants. Heat-related symptoms were assessed using validated questionnaires. Results: The level of occupational heat exposure was 72.4% (95% CI: 70.2%-74.8%), while 71.6% (95% CI: 69.3%-74.9%) of participants experienced at least one symptom related to heat stress. The most common heat-related symptoms were swelling of hands and feet (78%), severe thirst (77.8%) and dry mouth (77.4%). The identified risk factors were a lack of reflective shields (AOR: 2.20, 95% CI: 1.53, 3.17), not-enclosed extreme heat sources (AOR: 1.76, 95% CI: 1.23, 2.51), a lack of access to shade (AOR: 9.62, 95% CI: 6.20, 14.92), and inappropriate protective clothing provision (AOR: 1.58, 95% CI: 1.27, 2.71). Conclusions: The burden of occupational heat exposure and heat-induced symptoms was high. Lack of reflective shields, the absence of enclosed extreme heat sources, a lack of access to shade, and inappropriate protective clothing provision were considerable attributes of heat stress. Therefore, the use of mechanical solutions to stop heat emissions at their sources and the key factors identified were areas for future intervention.

• 한국심리학회지 : 문화 및 사회문제
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• 제11권spc호
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• pp.85-95
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• 2005

신뢰가 건강에 관련되는 기제를 정신-신체 의학 또는 통합의학적인 관점에서 살펴보았다. 이를 위해 양자물리학, 심신의학 및 동양의 치유방법 등의 연구성과를 알아보고 건강과 행복을 추구하는 방법도 제시하였다. 먼저, 콴툼 구조적인 사람의 몸에 관한 절에서는, 신체에는 그 자신의 정신이 있다는 연구 결과들을 알아보았는데, 여기서는 질병의 메커니즘과 원인, 의식의 객관적인 경험으로서의 몸, 의식과 정보에 영향 받는 몸 등을 다루었다. 그 다음에, 심신의학의 연구결과들을 다루었는데, 여기서는 뇌를 변화시키는 생각, 플라시보와 기대의 힘, 적극적인 노력으로 성취되는 건강, 심리신경면역학 및 치료방법들을 알아보았다. 끝으로, 몸과 마음의 행복을 위한 Benson의 실천방법을 알아보았는데, 병에서 회복하고 건강해지는데는 신념(자신에 대한 신념, 의사에 대한 신념, 치료에 대한 신념 및 자신의 영적인 신념)이 무엇보다도 중요하다는 결론에 이르렀다.

• Advances in nano research
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• 제15권3호
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• pp.215-224
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• 2023

Nonlinearity plays an important role in control systems and the application of design. For this reason, in addition to linear vibrations, nonlinear vibrations of the stepped nanobeam are also discussed in this manuscript. This study investigated the vibrations of stepped nanobeams according to Eringen's nonlocal elasticity theory. Eringen's nonlocal elasticity theory was used to capture the nanoscale effect. The nanoscale stepped Euler Bernoulli beam is considered. The equations of motion representing the motion of the beam are found by Hamilton's principle. The equations were subjected to nondimensionalization to make them independent of the dimensions and physical structure of the material. The equations of motion were found using the multi-time scale method, which is one of the approximate solution methods, perturbation methods. The first section of the series obtained from the perturbation solution represents a linear problem. The linear problem's natural frequencies are found for the simple-simple boundary condition. The second-order part of the perturbation solution is the nonlinear terms and is used as corrections to the linear problem. The system's amplitude and phase modulation equations are found in the results part of the problem. Nonlinear frequency-amplitude, and external frequency-amplitude relationships are discussed. The location of the step, the radius ratios of the steps, and the changes of the small-scale parameter of the theory were investigated and their effects on nonlinear vibrations under simple-simple boundary conditions were observed by making comparisons. The results are presented via tables and graphs. The current beam model can assist in designing and fabricating integrated such as nano-sensors and nano-actuators.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2020년도 춘계학술대회
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• pp.10-10
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• 2020

전 지구적으로 생물다양성의 지속적인 감소 추세에 따른 생물자원의 중요성이 증가하는 시점에서, 식물 유전자원의 종 다양성 보존과 지속가능한 이용을 위한 체계적이고 현실적인 방안 마련이 절실한 실정이다. 국내에서도 2017년에 유전자원 접근 및 이익 공유에 대한 나고야 의정서가 발효됨에 따라 식물유래 BT산업 소재의 국내 자급이 불가피해진 상황이며, 더불어 국토의 생태복원에 적합한 식물 소재 개발의 중요성이 대두되면서 자생식물의 종자 수급기반 대책은 국가적 차원에서 중대한 과제라 할 수 있다. 우리나라는 면적 대비 높은 식물 종 다양성을 보이며, 이는 종자의 휴면유형 또한 다양하고 복잡할 수 있다는 것을 의미한다. 따라서 식물유전자원으로써의 보존 및 국가 경제적 이익을 위한 종자 활용, 산업화를 위해서는 종자의 생리적 특성에 기반 한 데이터베이스의 축적과 효과적인 활용을 위한 종자 휴면유형 분류 및 적정 휴면타파 조건을 확립할 필요가 있다. 현재까지 다양한 식물종에서 종자 휴면의 하위 카테고리가 계속적으로 세부 분류되고 있으나, 아직까지 밝혀지지 않은 세부 휴면유형에 의해 많은 유용 식물자원의 활용이 제한적이다. 종자의 휴면유형은 크게 외생휴면(Exogenous dormancy)과 내생휴면(Endogenous dormancy)으로 분류되며, 국내에서는 내생휴면에 대한 연구가 주를 이루고 있다. 한편 외생휴면은 물리적 휴면(Physical dormancy), 기계적 휴면(Mechanical dormancy) 및 화학적 휴면(Chemical dormancy)으로 세부 분류되며, 기계적 휴면과 화학적 휴면은 내생휴면인 생리적 휴면(Physiological dormancy)에 포함되어야 한다는 의견도 있다. 물리적 휴면 종자에서는 water-gap 복합체의 존재 등에서 원인을 찾을 수 있으나, 발아억제 호르몬에 기인하는 화학적 휴면 및 종(과)피 또는 배유에 의한 기계적 휴면은 배의 성장잠재력과 발달에 의해 타파될 수 있다. 이와 같이 실제로 많은 식물 종에서 다양하게 존재하는 외생휴면 유형에 대해 내생휴면과는 명확히 다른 방식으로 접근되어야 하므로, 다년간의 체계적 연구를 통해 미흡한 종자생리 연구 분야를 보완하고 자생식물의 종자 활용도를 높일 수 있을 것으로 기대한다.

• Steel and Composite Structures
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• 제49권5호
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• pp.487-502
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• 2023

In the realm of nanotechnology, the nonlocal strain gradient theory takes center stage as it scrutinizes the behavior of spinning cantilever nanobeams and nanotubes, pivotal components supporting various mechanical movements in sport structures. The dynamics of these structures have sparked debates within the scientific community, with some contending that nonlocal cantilever models fail to predict dynamic softening, while others propose that they can indeed exhibit stiffness softening characteristics. To address these disparities, this paper investigates the dynamic response of a nonlocal cantilever cylindrical beam under the influence of external discontinuous dynamic loads. The study employs four distinct models: the Euler-Bernoulli beam model, Timoshenko beam model, higher-order beam model, and a novel higher-order tube model. These models account for the effects of functionally graded materials (FGMs) in the radial tube direction, giving rise to nanotubes with varying properties. The Hamilton principle is employed to formulate the governing differential equations and precise boundary conditions. These equations are subsequently solved using the generalized differential quadrature element technique (GDQEM). This research not only advances our understanding of the dynamic behavior of nanotubes but also reveals the intriguing phenomena of both hardening and softening in the nonlocal parameter within cantilever nanostructures. Moreover, the findings hold promise for practical applications, including drug delivery, where the controlled vibrations of nanotubes can enhance the precision and efficiency of medication transport within the human body. By exploring the multifaceted characteristics of nanotubes, this study not only contributes to the design and manufacturing of rotating nanostructures but also offers insights into their potential role in revolutionizing drug delivery systems.