• 한국지반신소재학회논문집
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• 제16권1호
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• pp.19-29
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• 2017

시멘트-점토-모래 혼합토의 휨성능 개선을 위하여 합성섬유를 이용해서 보강한 섬유보강토에 대한 휨성능 시험을 실시하였다. 시멘트, 모래, 그리고 섬유가 혼합토의 휨성능에 미치는 영향을 평가하기 위하여 시멘트량(15%, 20%, 25%), 모래함량(0%, 10%, 20%), 섬유의 종류(PP, PVA)와 길이(6mm, 12mm), 섬유혼입량(0.5%, 1.0%, 1.5%)을 조합하여 시험편을 제작하였다. 본 연구의 결과 시멘트 개량토를 섬유를 이용해서 보강하면 휨강도와 휨인성이 개선되는 효과를 확인할 수 있었다. 휨성능 시험 결과에 대한 다중선형회귀분석 결과 시멘트량과 모래함량은 휨강도에 영향을 미치는 주요 인자인 것으로 나타났고, 반면에 섬유혼입량은 균열발생 후의 거동에 영향을 미치는 주요 인자인 것으로 나타났다.

• Korean Chemical Engineering Research
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• 제50권5호
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• pp.783-788
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• 2012

스턴튜브베어링(Stern tube bearing))은 축계장치에서 축 회전 시 마찰을 줄이고 축의 무게를 지지하는 주요한 역할을 하는 부품임에도 불구하고 국산화가 이루어지지 않아 전량 수입에 의존하고 있어 국산화 개발이 요구되고 있다. 이에 국산화를 위한 스턴튜브 베어링용 폴리우레탄 수지를 개발할 목적으로 경도, 인장강도, 신장률에 미치는 첨가제의 영향을 조사하였다. 기본적으로 경화제 종류에 따라 MOCA Type과 Non-MOCA Type으로 구분하여 각각 폴리우레탄을 합성하고, 기본적 물성을 확인한 결과, Non MOCA Type은 경도 23 D, 인장강도 4.3 Mpa로 본 연구의 목표치에 훨씬 미치지 못하는 것으로 나타났으며, 반면에 MOCA Type의 폴리우레탄 수지는 기계적 강도가 높은 것으로 나타나 전반적으로 MOCA Type의 폴리우레탄수지를 기본 수지로 사용하여 연구를 진행하였다. 기본적인 폴리우레탄 수지의 합성은 폴리올에 MOCA를 23.0 wt%로 첨가하고, 1차 경화는 $110^{\circ}C$에서 1시간 경화하고, $110^{\circ}C$에서 15시간 2차 경화를 하여 수지를 제조하였다. 첨가제로는 그래파이트, 칼슘카보네이트, 카본블랙, 실리카를 각각 사용하여, 이들 첨가제의 종류와 첨가량에 따라 경도, 인장강도, 신장률에 미치는 효과에 대한 실험을 수행하여 실리카를 첨가한 폴리우레탄 수지는 경도, 인장강도가 비교적 우수하면서도 신장률도 다소 증가하는 폴리우레탄 수지를 제조할 수 있었다.

• Asian-Australasian Journal of Animal Sciences
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• 제20권5호
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• pp.706-710
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• 2007

This study was to investigate the caponization effects on bone characteristics in male chickens, and the optimum testosterone implantation dosage on bone characteristics improvement. Healthy Single Comb White Leghorn cockerels were caponized at 12-wk-old and selected at 16-wk-old for a 10-wk feeding experiment. Fifteen intact male and caponized male chickens (capon) respectively were assigned to trial 1. Ten sham-operated chickens and 40 capons (randomly allocated into four treatments) were implanted with cholesterol (1.62 mm i.d., 3.16 mm o.d., $9.24{\pm}0.36$ mg), low (1 mm i.d., 3 mm o.d., $5.88{\pm}0.23$ mg), medium (1.62 mm i.d., 3.16 mm o.d., $9.81{\pm}0.17$ mg) or high dose (2 mm i.d., 4 mm o.d., $16.7{\pm}0.24$ mg) of testosterone in trial 2. The results from trial 1 showed that the tibia length, relative tibia weight, breaking strength, bending moment and stress in intact males were higher than capons (p<0.05). The blood phosphorus concentration in capons was higher than the intact male chickens (p<0.05). Caponization also resulted in more antrums and osteoclasts within periosteum and cortical bone from histological observation. In trial 2, the adverse impact of caponization on the bone breaking strength, bending moment and stress could be alleviated through medium dose testosterone implantation. It appears that caponization reduced androgen secretion hence influenced the biomechanical characteristics of bone (tibia) and these adverse effects could be alleviated through appropriate dose of testosterone implantation.

• Journal of Forest and Environmental Science
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• 제31권2호
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• pp.119-125
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• 2015

This study examined the effects of rice straw steaming time and mixing ratio between rice straw and wood particle on the properties of mixed particle board from Acacia mangium Willd wood and rice straw. Rice straw and Acacia mangium Willd wood were collected in Hanoi, Vietnam. The particle board was three-layer particle board with the structural ratio of 1:3:1. The thickness, density and board size of the particle board were 18 mm, $0.7g/cm^3$, and $800{\times}800{\times}18$ (mm, including trimming), respectively. A resin mixture between commercial Urea-formaldehyde (U-F) adhesive and methylene diphenyl isocyanate (MDI) adhesive was used with a dosage of 12% for the core layer and 14% for the surface layer. In this experimental design, the steaming time for rice straw was 15, 30, 45, 60, and 75 minutes at $100^{\circ}C$. The rice straw-wood mixing ratio was 10, 20, 30, 40, and 50%. The results showed that both mixing ratio and steaming time affect the properties of the particleboard, but the mixing ratio has a stronger impact. A higher mixing ratio and a longer steaming time resulted in a better quality of particleboard. The optimal steaming time for rice straw was 46.12 minutes with the straw-wood mixing ratio of 29.85% with the following characteristics of the particle board: the modulus of rupture (MOR) of 14.64 MPa, internal bond strength (IB) of 0.382 MPa, thickness swelling (TS) of 8.83%, and board density of $0.7-0.7g/cm^3$.

• Archives of Pharmacal Research
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• 제26권2호
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• pp.162-167
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• 2003

Liquid suppository systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and mucoadhesive to the rectal tissues without leakage after the dose. However, a liquid suppository containing diclofenac sodium could not be developed using bioadhesive polymers. since the drug was precipitated in this preparation. To develop a liquid suppository system using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the liquid suppository was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The liquid suppositories with less than 1.0％ of sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage. Furthermore, liquid suppository gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from liquid suppository could be absorbed faster than that from solid one in rats. Our results suggested that a thermosensitive liquid suppository system with sodium chloride and poloxamers was a more physically stable, convenient and effective rectal dosage form for diclofenac sodium.

• 약학회지
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• 제42권2호
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• pp.187-195
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• 1998

In order to ameliorate disadvantages of buccal ointments and mucoadhesive tablets used for the treatment of aphthosis, a thin mucoadhesive patch containing triamcinolone acetoni de was designed and evaluated for the pharmaceutical properties. The adhesive gel layer consisting of Noveon AA-1, hydroxypropylcellulose-M and ethylcellulose N 100, and the protective gel layer of ethylcellulose N 100, Eudragit RSPO and castor oil have been formulated and various properties such as viscosity of drug gel layer, thickness, in vitro adhesion time, adhesive strength, surface pH, content uniformity and drug release are tested. The mean viscosity of drug-containing gel layer was found to increase with increasing amount of Noveon OAA-1 or hydroxypropylcellulose-M. The optimum formulation showed the thickness of 171 ${\mu}$m, surface pH of 4.6, in vitro adhesion time of 8 hours and adhesive strength of 272.7g/sheet. The drug content of each patch was relatively homogeneous with the value of 273${\pm}$6.77g. Drug release study showed that compared to mucoadhesive tablet, the patch showed a faster drug release. Drug release was delayed by hydroxypropylcellulose-M, but not by ethylcellulose N 100. The patches prepared were nonirritant and the muco adhesion was better than the commercial product (AftachR) on the market. Based on these results, this mucoadhesive patch is expected to be an effective dosage form for the treatment of aphthosis.

• Advances in environmental research
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• 제10권1호
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• pp.59-86
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• 2021

Landfilling is the most commonly adopted method for a large quantity of waste disposal. But, the main concern related to landfills is the generation of leachate. The leachate is high strength wastewater that is usually characterized by the presence of high molecular recalcitrant organics. Several conventional methods are adopted for leachate treatment. However, these methods are only suitable for young leachate, having high biodegradability and low toxicity levels. The mature and stabilized leachate needs advanced technologies for its effective treatment. Advanced oxidation processes (AOPs) are very suitable for such complex wastewater treatment as reported in the literature. After going through the literature survey, it can be concluded that Fenton-based approaches are effective for the treatment of various high/low strength wastewaters treatment. The applications of the Fenton-based approaches are widely adopted and well recognized due to their simplicity, cost-effectiveness, and reliability for the reduction of high chemical oxygen demand (COD) as reported in several studies. Besides, the process is relatively economical due to fewer chemical, non-sophisticated instruments, and low energy requirements. In this review, the conventional and advanced Fenton's approaches are explained with their detailed reaction mechanisms and applications for landfill leachate treatment. The effect of influencing factors like pH, the dosage of chemicals, nature of reaction matrix, and reagent ratio on the treatment efficiencies are also emphasized. Furthermore, the discussion regarding the reduction of chemical oxygen demand (COD) and color, increase in biodegradability, removal of humic acids from leachate, combined processes, and the pre/post-treatment options are highlighted. The scope of future studies is summarized to attain sustainable solutions for restrictions associated with these methods for effective leachate treatment.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2004년도 학술.기술논문발표회
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• pp.61-64
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• 2004

This study is to investigate the engineering and shrinkage properties of concrete incorporating shrinkage reducing agent(SRA) and expansive additive(EA) in order to reduce shrinkage of concrete. According to results, as for the properties of fresh concrete, increase in, SRA and EA content leads to reduce the fluidity but to increase the air content, and as for setting time, there is little difference. For strength properties, it decreased with an increase in SRA dosage and increased up to 5% of EA content. For the properties of drying shrinkage, it shows decline tendency with an increase in SRA and EA content reiteratively. It alto reduces significantly with the combination of SRA-EA systems due to the combined effect of the admixture. In the scope of this paper, it is found that the use of SRA with 0.5％ and EA with 5% has optimum effects on the various properties of concrete. And under the combination of SRA and EA, it can reduce drying shrinkage about 37%.

• Steel and Composite Structures
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• 제19권1호
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• pp.153-171
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• 2015

Twelve large-scale composite deck slabs were instrumented and tested in a cantilever diaphragm configuration to assess the effect of fibers and welded wire mesh (WWM) on the in-plane shear capacity of composite deck slabs. The slabs were constructed with reentrant decking profile and reinforced with different types and dosages of secondary reinforcements: Conventional welded wire mesh (A142 and A98); synthetic macro-fibers (dosages of $3kg/m^3$ and $5.3kg/m^3$); and hooked-end steel fibers with a dosage of $15kg/m^3$. The deck orientation relative to the main beam (strong and weak) was also considered in this study. Fibers and WWM were found efficient in distributing the applied load to the whole matrix, inducing multiple cracking, thereby enhancing the strength and ductility of composite deck slabs. The test results indicate that fibers increased the slab's ultimate in-plane shear capacity by up to 29% and 50% in the strong and weak directions, respectively. WWM increased the ultimate in-plane shear capacity by up to 19% in the strong direction and 9% in the weak direction. The results suggest that discrete fibers can provide comparable diaphragm behavior as that with the conventional WWM.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2010년도 춘계학술발표회 논문집
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• pp.195-206
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• 2010

Xylan can be applied to improve the strength properties of paper; however the optical properties, such as brightness, are decreased significantly. To solve that problem, an applicable bleaching process is therefore desired. The aim of this research was to investigate the impact of hydrogen peroxide bleaching on hardwood kraft pulp pretreated with birchwood xylan by measuring optical properties (whiteness, brightness, opacity) as well as physical properties (tensile index, tearing index, bulk) of handsheets made from the bleached pulp. Hydrogen peroxide bleaching, as a kind of totally chlorine free (TCF) bleaching method, is quite important industrially for chemical pulp. In our work, the process variables of peroxide bleaching including bleaching temperature, time, initial pH and $MgSO_4$ dosage were studied. The results showed that both good mechanical properties and optical properties could be achieved when the operating parameters were controlled properly and therefore hydrogen peroxide bleaching was proved to be a suitable method for bleaching hardwood kraft pulp with adsorption of birchwood xylan.