• 대한토목학회논문집
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• 제43권5호
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• pp.555-566
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• 2023

본 연구에서는 콘크리트 부재에 저온 적용을 위해 SOL-GEL 기법을 이용하여 제조된 열에너지 저장 복합상변화물질(CPCM)를 개발하였다. 코어는 테트라데칸, 지지재는 활성탄(AC)을 각각 사용하였다. 진공 함침법을 이용하여 AC의 다공성 구조에 테트라데칸 상변화 물질(PCM)을 함침시키고, 테트라에틸오르토실리케이트(TEOS)를 사용한 SOL-GEL 공정을 이용하여 제조된 복합체에 실리카 겔을 얇게 코팅하였다. CPCM의 열 성능은 시차주사열량계(DSC)과 열 중량분석(TGA)을 통해 분석했다. DSC 결과 테트라데칸 PCM은 용융 및 동결 온도가 각각 6.4℃ 및 1.3℃이고 해당 엔탈피는 각각 226J/g 및 223.8J/g인 것으로 나타났다. CPCM은 7.1℃ 및 2.4℃에서 용융 및 동결 과정에서 각각 32.98J/g 및 27.7J/g의 엔탈피를 나타내었다. TGA 시험 결과 AC는 500℃까지 열적으로 안정하며, 이는 120℃ 정도인 순수 테트라데칸의 분해 온도보다 훨씬 높은 것으로 나타났다. 또한, AC-PCM과 CPCM의 경우 각각 80℃와 100℃에서 열분해가 시작되었다. CPCM의 화학적 정성 분석을 위해 푸리에 변환 적외선(FT-IR) 분광법을 이용하였으며, 그 결과 개발된 복합체가 화학적으로 안정함을 확인하였다. 마지막으로, SOL-GEL 공정 후 AC 표면에 실리카 겔의 얇은 층이 존재함을 확인하기 위해 주사전자현미경(SEM)을 이용하여 AC와 CPCM의 표면 형태를 분석하였다.

• 한국초등과학교육학회지:초등과학교육
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• 제42권1호
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• pp.47-63
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• 2023

이 연구에서는 2015 개정 교육과정에 따른 초등학교 과학과 검정 교사용 지도서의 3~4학년 물질 영역에 나타난 PCK 요소를 분석하였다. 2009 개정 교육과정에 따른 중학교 교사용 지도서와 달리 상대적으로 PCK 요소의 편차가 작았다. 평균적으로 과학 내용에 관한 지식이 가장 높은 비율을 차지하였고, 과학 교수 전략에 관한 지식이 과학 교육과정에 관한 지식보다 비율이 높게 다뤄졌다. 과학 평가에 관한 지식은 출판사 간 편차가 가장 컸으며, 학생에 관한 지식은 대부분의 출판사에서 비율이 낮게 나타났다. 하위요소로는 개념 및 이론보다 실험 및 탐구의 비율이 높았다. 수직 연계와 수업 목표에 비해 수평연계의 비율이 낮았고, 수업 목표는 교과 역량, 성취기준 등으로 다양하게 제시되었다. 발문이 강조됨에 따라 지도 전략과 발문이 비슷한 비율로 나타났다. 동기 및 흥미, 오개념은 지도 전략, 발문과의 연계가 나타났다. 평가 문항과 평가 준거는 수준별로 제시된 경우가 있었으며, 이 두 요소를 중심으로 다양한 PCK 요소의 연계가 있었다. 출판사별 편차가 상대적으로 큰 요소는 보충·심화 개념, 교과서 탐구, 활동 순서 및 방식, 교과 특이적 전략, 평가 문항이었다. 이상의 연구 결과를 중심으로 추후 교사용 지도서 개발을 위한 시사점을 논의하였다.

• 대한토목학회논문집
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• 제28권3C호
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• pp.149-158
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• 2008

본 연구에서는 수치해석을 통하여 국내 해상 장대교량의 기초로 사용된 대구경 현장타설말뚝의 거동특성을 분석하고 외부 강관케이싱에 의한 말뚝의 지지력 증진효과를 검증하고자 한다. 직경이 다른 3종류의 현장타설말뚝에 대하여 1) 외부강관이 없는 경우, 2) 외부강관이 있는 경우 그리고 3) 외부강관과 콘크리트가 일체화 거동을 하는 경우 등 3가지 모델을 설정하고 3차원 유한요소해석을 수행하였다. 강관과 콘크리트사이에는 경계면 요소(interface)를 적용하였으며, 지반 및 하중조건은 현장의 조건을 사용하였다. 각 모델에 대한 세부적인 변위 및 응력분석을 통하여 강관합성 현장타설말뚝의 거동특성을 파악하였다. 수치해석결과 본 해석에서 선정한 대구경 현장타설말뚝의 경우 외부강관을 구조재로 고려하는 경우 동일 하중조건에 대한 수평변위 및 수직변위가 각각 32~37%와 15~19% 정도 감소되는 것으로 나타났다.

• 한국건축시공학회지
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• 제23권5호
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• pp.537-546
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• 2023

국내 건축물의 방화구획에 사용되는 철강재 벽체는 품질시험 등을 거쳐 내화구조로 인정받은 경우에만 사용할 수 있다. 품질시험은 내화 및 부가 시험으로 이루어지는데 철강재 벽체의 부가 시험 항목은 가스유해성과 휨강도이다. 가스 유해성의 경우 준불연 심재 사용으로 인하여 실질적으로 생략되므로 내화구조 인정 과정의 부가시험은 휨강도만 실시하는 셈이다. 휨강도의 경우 벽체를 구성하는 단위 판의 강도를 측정하는데, 특정 강도 이상으로 명시되어 인정되기에 강도가 높으면 내화시험 시 시험체 변형에 저항하여 차염성과 차열성을 확보하는데 유리할 것으로 예상해 볼 수 있다. 이에 현재 인정이 유효한 1시간용 건축용 철강재 벽체구조의 인정 당시 시험 데이터를 분석하여 내화성능과 휨강도가 유의한 관계가 있는지 살펴본 결과, 양자 간에 통계적으로 유의한 관계는 없는 것으로 나타났다.

• Korean Journal of Radiology
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• 제24권9호
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• pp.903-911
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• 2023

Objective: Regrowth after radiofrequency ablation (RFA) of symptomatic large thyroid nodules, initially treated as benign, sometimes turns out to be malignancies. This study aimed to assess the ultrasound (US) characteristics of thyroid nodules initially treated as benign with RFA and later diagnosed as cancers, predictive factors for cancers masquerading as benign, and methods to avoid RFA in these cancers. Materials and Methods: We reviewed the medical records of 134 consecutive patients with 148 nodules who underwent RFA between February 2008 and November 2016 for the debulking of symptomatic thyroid nodules diagnosed as benign using US-guided biopsy. We investigated the pre-RFA characteristics of the thyroid nodules, changes at follow-up after RFA, and the final surgical pathology. Results: Nodule regrowth after RFA was observed in 36 (24.3%) of the 148 benign nodules. Twenty-two of the 36 nodules were surgically removed, and malignancies were confirmed in seven (19.4% of 36). Of the 22 nodules removed surgically, pre-RFA median volume (range) was significantly larger for malignant nodules than for benign nodules: 22.4 (13.9-84.5) vs. 13.4 (7.3-16.8) mL (P = 0.04). There was no significant difference in the regrowth interval between benign and malignant nodules (P = 0.49). The median volume reduction rate (range) at 12 months was significantly lower for malignant nodules than for benign nodules (51.4% [0-57.8] vs. 83.8% [47.9-89.6]) (P = 0.01). The pre-RFA benignity of all seven malignant nodules was confirmed using two US-guided fine-needle aspirations (FNAs), except for one nodule, which was confirmed using US-guided core-needle biopsy (CNB). Regrown malignant nodules were diagnosed as suspicious follicular neoplasms by CNB. Histological examination of the malignant nodules revealed follicular thyroid carcinomas, except for one follicular variant, a papillary thyroid carcinoma. Conclusion: Symptomatic large benign thyroid nodules showing regrowth or suboptimal reduction after RFA may have malignant potential. The confirmation of these nodules is better with CNB than with FNA.

• Composites Research
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• 제37권3호
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• pp.219-225
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• 2024

정찰위성의 탑재체인 위성용 전개형 반사판 안테나는 발사 환경에 대한 구조안정성 및 궤도 환경에 대한 운용 성능을 고려하여 경량화, 고성능의 구조 개발이 필수적이다. 그 중, 복합재 주반사판은 전개형 반사판 안테나를 구성하는 핵심 구성품이며, 발사체 탑재 성능을 고려한 경량 설계 뿐만 아니라 위성체 임무 수행 중 민첩한 자세제어 기동 이후 높은 품질의 위성 영상을 획득하기 위해서는 높은 전개 시 강성을 갖는 고성능의 주반사판 개발이 요구된다. 주반사판 개발을 위해 전개형 반사판 안테나를 구성하는 복합재 주반사판의 적층 설계 및 재료 물성에 따른 구조적 성능을 분석하여 주반사판의 초기 설계안을 도출하였으며, 도출된 초기 설계안을 기준으로 제작 공정을 변수로 4가지 타입의 복합재 주반사판을 제작하였다. 공정 변수로는 복합재 구조의 성형 공정, 탄소 섬유 복합재 시트와 허니콤 코어 간 접착 필름의 적용 유/무, 샌드위치 복합재 내부의 벤팅 경로를 선정하였다. 제작된 4가지 종류의 주반사판에 대해 무게 측정, 비파괴 검사, 표면오차 측정 및 모드 시험을 통한 전개 시 강성 측정을 수행하였으며, 경량 및 구조적 성능을 향상시킬 수 있도록 접착 필름을 미적용하며 벤팅 경로를 포함하는 주반사판 제작 공정을 선정하여 SAR(합성 개구 안테나)를 포함한 위성체에 실 적용이 가능한 복합재 주반사판을 개발하였다.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4447-4464
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• 2023

This paper focuses on the development of a new computational model of the CNESTEN's TRIGA Mark II research reactor using the 3D continuous energy Monte-Carlo code TRIPOLI-4 (T4). This new model was developed to assess neutronic simulations and determine quantities of interest such as kinetic parameters of the reactor, control rods worth, power peaking factors and neutron flux distributions. This model is also a key tool used to accurately design new experiments in the TRIGA reactor, to analyze these experiments and to carry out sensitivity and uncertainty studies. The geometry and materials data, as part of the MCNP reference model, were used to build the T4 model. In this regard, the differences between the two models are mainly due to mathematical approaches of both codes. Indeed, the study presented in this article is divided into two parts: the first part deals with the development and the validation of the T4 model. The results obtained with the T4 model were compared to the existing MCNP reference model and to the experimental results from the Final Safety Analysis Report (FSAR). Different core configurations were investigated via simulations to test the computational model reliability in predicting the physical parameters of the reactor. As a fairly good agreement among the results was deduced, it seems reasonable to assume that the T4 model can accurately reproduce the MCNP calculated values. The second part of this study is devoted to the sensitivity and uncertainty (S/U) studies that were carried out to quantify the nuclear data uncertainty in the multiplication factor k_eff. For that purpose, the T4 model was used to calculate the sensitivity profiles of the k_eff to the nuclear data. The integrated-sensitivities were compared to the results obtained from the previous works that were carried out with MCNP and SCALE-6.2 simulation tools and differences of less than 5% were obtained for most of these quantities except for the C-graphite sensitivities. Moreover, the nuclear data uncertainties in the k_eff were derived using the COMAC-V2.1 covariance matrices library and the calculated sensitivities. The results have shown that the total nuclear data uncertainty in the k_eff is around 585 pcm using the COMAC-V2.1. This study also demonstrates that the contribution of zirconium isotopes to the nuclear data uncertainty in the k_eff is not negligible and should be taken into account when performing S/U analysis.

• 한국인쇄학회지
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• 제30권3호
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• pp.89-114
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• 2012

For as to world, the concern about the environment problem is enhanced than any other time in the past because of being 21 century. And the environment problem is highlighted as the world-wide issue. The time of the environment problem intimidates the alive of the mankind and presence of an earth over the time. It becomes the essentiality not being selection in the personal living or the economical viewpoint now to prepare for the climatic modification. As to the company management, the green growth period which it excludes the environment management considering an environment, cannot carry on the company the continued management comes. That is, in the change center of the management paradigm, there is the environment management. Nearly, the greenhouse gas which the publication industry is the environmental toxic material like all industries is generated. The greenhouse gas is ejected in the process of running the manufacturing process and print shop of the various kinds material used as the raw material of the book. Particularly, the tree felling for getting the material of the paper is known to reach the direct influence on the global warming. This study does according to an object it considers and organizes the environment parameter based on this kind of fact as to the publication industry. And it is determined as the reference which is used as the basic materials preparing the case that carbon exhaust right transaction(CAP and TRADE) drawing are enforced in all industries and is sustainable the management of the publication industry and reduces the environmental risk among the company many risk management elements and plans and enforces the publication related policy that there is a value. In the printing publication industry, this study tried to inquire into elements discharging the environmental pollutant or the greenhouse gas. Additionally, in the printed publication production process, it tried to inquire into the effort for an environment-friendly and necessity at the printing paper and the printers ink, regarded as the element discharging the greenhouse gas all kinds of the printing materials, operation of the print shop and all kinds of the machines and recycle process, and etc. These considerations make these industrial field employees aware of the significance about a conservation and environmental protection. They try to give a help in the subsequent study producing quantitatively each environmental parameter emission of green house gas. This makes the calculation of the relative $CO_2$ output reproached ultimately possible. Meanwhile, in a sense, many research protects and improving an environment in connection with the contents of research at the printing publication industrial field is in progress. There will be the voluntary human face that it has to protect an environment but this can not do by the outside factor according to all kinds of environment related law and regulation. Anyway, because of acting on company management as the factor of oppression, the increase of this environment-related correspondence cost could know that the research that the environment loading relates with a procurement and development, environment management system introduction, quality control standard, including, normalizing including a material, and etc. through the part of the effort to reduce the cost low was actively in progress. As to the green growth era, as follows, this paper prescribed the subject and alternative of the print publication industry. It is surrounded by the firstly new digital environment and the generation of the subject. And secondly the printing industry is caused by the point of time when the green growth leaves by the topic which is largest in the global industry and it increases. The printing publication industry has to prepare the bridgehead for the environment-friendly green growth as the alternative for this resolution with first. The support blown in each industry becomes the obligation not being selection. Prestek in which the print publishing was exposed to spend many energies and which is known as the practice of the sustainable print publishing insisted that it mentioned importance of the green printing through the white pages in 2008 and a company had to be the green growth comprised through the environment-friendly activity. The core management for the sustainable printing publication industry presented from Presstack white pages is compacted to 4 words that it is a remove, reduce, recover, and recycle. Second, positively the digital printing(POD) system should be utilized. In the worldwide print out market, the digital printing area stops at the level of 10% or so but the change over and growth of the market of an analog-to-digital will increase rapidly in the future. As to the CEO Jeff Hayes of the Infoland, the offset print referred to that it of the traditional method got old and infirm with the minor phase of the new printing application like the customer to be wanted publication and the print of the digital method led the market. In conclusion, print publishers have to grasp well the market flow in the situation where a digitalization cannot be generalized and a support cannot avoid. And it keeps pace with the flow of the digital age and the recognition about the effort for the development and environment problem have to be raised. Particularly, the active green strategy is employed for the active green strategy.

• 한국과학교육학회지
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• 제34권5호
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• pp.437-447
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• 2014

Learning Progressions(학습진행과정, 이하 LP)은 "과학의 핵심 아이디어(core idea) 혹은 과학 활동(scientific practices) 이해 과정을 상대적으로 단순한 체계에서 전문가의 지식체계로 논리적이고, 순차적인 단계로 정교하게 설명한 틀"로서, 한 교과 내 및 다른 과학영역들(물리, 지구과학, 생물, 화학)과 연결하여 연계적 교육과정을 구성하는 이론적 기반을 제공한다. 학습은 개개인의 선지식, 선경험, 교과교육과정, 교육과정 등의 여러 요소에 영향을 받는 복잡한 이해 과정으로, LP 단계를 모든 학생들이 동일하게 이동하지 않는다. 학생과 학습환경의 특성에 따른 이동 가능한 학습경로의 서술을 위해서는 다양한 학생데이터의 수집과 분석이 필요하다. 이러한 과정을 통해서 가설의 LP는 과학적으로 증명된 LP로 규명되며. 비로소 교과과정 개발의 틀(framework)로 역할을 할 수 있다. 본 연구는 미시간 대학 연구팀이 개발한 "물질의 본성(nature of matter)" 주요 개념에서, 하위개념인 "물질의 입자성(particule nature of matter)과 입자적 표상(submicroscophic representation)"의 LP와 관련 평가지를 우리나라 과학교육과정과 연계, 수정하여 개발하였다. 수정된 평가지와 LP는 124명의 중고등학생의 LP 경로 특성을 분석하는데 사용되었다. 학생들의 입자적 개념과 표상의 이해도, 개념과 표상 이해도 연관성을 중점으로 분석하여 관련 과학교육과정과 현장 수업의 문제점과 시사점을 도출하였다. 본 연구결과를 종합해 보면, 높은 레벨 문항의 정답을 고른 빈도수는 낮은 레벨 문항을 모두 정답으로 고른 경우에 높았으며 이는 학생들이 본 연구팀이 개발한 LP 경로로 이해과정을 정교화시킴을 알 수 있다. 하지만, 대부분의 학생들, 특히 고등학생들은 초등학교 수준의 거시적 물질의 본성 개념 LP 단계에 머물고 있으며, 중학교 수준인 미시적 표상 LP 단계에 있다. 입자적 개념과 표상 이해 실패의 주요 원인은 1) 과학적 모델의 본질, 2) 관련 선지식, 3) 미립자 표상의 이해부족으로 정리된다. 본 연구결과는 물질의 입자성과 관련된 개념, 과학활동(특히 모델링)을 증진시키고 개개인 특성에 맞는 맞춤형 학습환경 제공을 위한 학습, 교수, 평가자료 개발에 기여하는 바가 크다. 더 나아가 '물질의 본성'에 대한 LP연구와 과학적 소양 증진에 긍정적 역할을 할 것으로 기대한다.

• 한국식품영양학회:학술대회논문집
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• 한국식품영양학회 2001년도 동계 학술심포지움
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• pp.39-74
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• 2001

The endeavors enhancing the grain quality of high-yielding japonica rice were steadily continued during 1980s∼1990s along with the self-sufficiency of rice production and the increasing demands of high-quality rices. During this time, considerably great, progress and success was obtained in development of high-quality japonica cultivars and qualify evaluation techniques including the elucidation of interrelationship between the physicochemical properties of rice grain and the physical or palatability components of cooked rice. In 1990s, some high-quality japonica rice caltivars and special rices adaptable for food processing such as large kernel, chalky endosperm aromatic and colored rices were developed and its objective preference and utility was also examined by a palatability meter, rapid-visco analyzer and texture analyzer. The water uptake rate and the maximum water absorption ratio showed significantly negative correlations with the K/Mg ratio and alkali digestion value(ADV) of milled rice. The rice materials showing the higher amount of hot water absorption exhibited the larger volume expansion of cooked rice. The harder rices with lower moisture content revealed the higher rate of water uptake at twenty minutes after soaking and the higher ratio of maximum water uptake under the room temperature condition. These water uptake characteristics were not associated with the protein and amylose contents of milled rice and the palatability of cooked rice. The water/rice ratio (in w/w basis) for optimum cooking was averaged to 1.52 in dry milled rices (12% wet basis) with varietal range from 1.45 to 1.61 and the expansion ratio of milled rice after proper boiling was average to 2.63(in v/v basis). The major physicochemical components of rice grain associated with the palatability of cooked rice were examined using japonica rice materials showing narrow varietal variation in grain size and shape, alkali digestibility, gel consistency, amylose and protein contents, but considerable difference in appearance and torture of cooked rice. The glossiness or gross palatability score of cooked rice were closely associated with the peak. hot paste and consistency viscosities of viscogram with year difference. The high-quality rice variety “Ilpumbyeo” showed less portion of amylose on the outer layer of milled rice grain and less and slower change in iodine blue value of extracted paste during twenty minutes of boiling. This highly palatable rice also exhibited very fine net structure in outer layer and fine-spongy and well-swollen shape of gelatinized starch granules in inner layer and core of cooked rice kernel compared with the poor palatable rice through image of scanning electronic mcroscope. Gross sensory score of cooked rice could be estimated by multiple linear regression formula, deduced from relationship between rice quality components mentioned above and eating quality of cooked rice, with high Probability of determination. The ${\alpha}$ -amylose-iodine method was adopted for checking the varietal difference in retrogradation of cooked rice. The rice cultivars revealing the relatively slow retrogradation in aged cooked rice were Ilpumbyeo, Chucheongbyeo, Sasanishiki, Jinbubyeo and Koshihikari. A Tongil-type rice, Taebaegbyeo, and a japonica cultivar, Seomjinbyeo, shelved the relatively fast deterioration of cooked rice. Generally, the better rice cultivars in eating quality of cooked rice showed less retrogiadation and much sponginess in cooled cooked rice. Also, the rice varieties exhibiting less retrogradation in cooled cooked rice revealed higher hot viscosity and lower cool viscosity of rice flour in amylogram. The sponginess of cooled cooked rice was closely associated with magnesium content and volume expansion of cooked rice. The hardness-changed ratio of cooked rice by cooling was negatively correlated with solids amount extracted during boiling and volume expansion of cooked rice. The major physicochemical properties of rice grain closely related to the palatability of cooked rice may be directly or indirectly associated with the retrogradation characteristics of cooked rice. The softer gel consistency and lower amylose content in milled rice revealed the higher ratio of popped rice and larger bulk density of popping. The stronger hardness of rice grain showed relatively higher ratio of popping and the more chalky or less translucent rice exhibited the lower ratio of intact popped brown rice. The potassium and magnesium contents of milled rice were negatively associated with gross score of noodle making mixed with wheat flour in half and the better rice for noodle making revealed relatively less amount of solid extraction during boiling. The more volume expansion of batters for making brown rice bread resulted the better loaf formation and more springiness in rice bread. The higher protein rices produced relatively the more moist white rice bread. The springiness of rice bread was also significantly correlated with high amylose content and hard gel consistency. The completely chalky and large gram rices showed better suitability for fermentation and brewing. Our breeding efforts on rice quality improvement for the future should focus on enhancement of palatability of cooked rice and marketing qualify as well as the diversification in morphological and physicochemical characteristics of rice grain for various value-added rice food processings.