• 콘크리트학회논문집
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• 제12권3호
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• pp.47-55
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• 2000

Protections from the frost damage at early ages are one of the serious problems to be considered in cold weather concreting. Frost damage at early ages brings about the harmful influences on the concrete structures such as surface cracks and declination of strength development. Therefore, in this paper, protecting periods of frost damage at early ages according to the standard specifications provided in KCI(Korean Concrete Institute) are suggested by appling logistic curve, which evaluates the strength development of concrete with maturity. W/B, kinds of cement and curing temperatures are selected as test parameters. According to the results, the estimation of strength development by logistic curve has a good agreement between calculated values and measured values. As W/B and compressive strength for protecting from frost damages at early ages increase, it is prolonged. It shows that the protecting periods of FAC(Fly Ash Cement) and BSC(Blast-furnace Slag Cement) concrete are longer than those of OPC(Ordinary Portland Cement) concrete. The protecting peridos from frost damage at early age by JASS are somewhat shorter than those by this paper.

• Steel and Composite Structures
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• 제7권2호
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• pp.135-160
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• 2007

Recently, CFT column has been well-studied and reported on, because a CFT column has certain superior structural properties as well as good productivity, execution efficiency, and improved rigidity over existing columns. However, CFT column still has problems clearing the capacity evaluation between its steel tube member and high-strength concrete materials. Also, research on concrete has examined numerical values for high-strength concrete filled steel square tube columns (HCFT) to explain transformation performance (M-${\phi}$) when a short-column receives equal flexure-moment from axial stress. Moment-curvature formulas are proposed for HCFT columns based on analytic assumption described in this paper. This study investigated structural properties (capacity, curvature), through a series of experiments for HCFT with key parameters, such as strength of concrete mixed design (58.8 MPa), width-thickness ratio (D/t), buckling length to sectional width ratio (Lk/D) and concrete types (Zeolite, Fly-ash, Silica-fume) under eccentric loads. A comparative analysis executed for the AISC-LRFD, AIJ and Takanori Sato, etc. Design formulas to estimate the axial load (N)-moment (M)-curvature (${\phi}$) are proposed for HCFT columns based on tests results described in this paper.

• 펄프종이기술
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• 제43권2호
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• pp.1-8
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• 2011

The presence of high silica in bamboo hinders the use of this material for production of rayon grade pulp. Research has been carried out to overcome this deficiency and improve quality of rayon grade pulp with the modification in pulping and bleaching process. Effect of acid boosted water prehydrolysis, sulphuric acid pre-treatment of unbleached pulp, chlorination stage at lower pH and treatment of bleached pulp with $SO_2$ water were evaluated. Acid boosted water prehydrolysis of chips reduces prehydrolysis time by 50 minutes as compared to water prehydrolysis. Treatment of unbleached pulp with sulphuric acid reduces ash, acid insoluble, silica, calcium and iron contents of the pulp by 56, 31, 82, 84 and 60% respectively. The addition of acid, increase in kappa factor in $C_D$ stage and combination of both were effective in removing silica in the pulp. Treatment of final bleached pulp with $SO_2$ water removes silica to a great extent and improves optical properties of the pulp as compared to $H_2SO_4$ or PAA. Pretreatment of the pulp with acid and modification in the bleaching process can reduce silica substantially and improve the quality of rayon grade bamboo pulp.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.108.1-108.1
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• 2011

This paper proposes the method to develop the fuel of suljigemi pellets using agricultural by-products the occurred during the manufacturing of alcohol. This paper is the goal to make sulgigemi pellet fuel for develops pellet of high calorie. The methods of sulgigemi pellet manufacturing well mix as the dough with the water and the sulgigemi. And then we have dried in the after compression and molding using well mixed the sulgigemi. The moisture of pellets has dried it removed until about 85%. Suljigemi pellet has the effect of zero emission as the soil conditioner using ash after burning. The merits for the sulgigemi pellet are the convenience of storage and custody. Also sulgigemi pellet has the reduction effect of carriage fee, fuel economy and low-cost high-efficiency effects, environmentally clean fuel as CO2 emissions savings. In experiment, we confirmed to calories of the wood pellet and the sulgigemi pellet. The calorie of the suljigemi pellets has high 233 kilo calories than the wood pellets. So the technologies of the sulgigemi fuel pellets are developing low carbon, green growth renewable energy fuel through futuristic energy system will be.

• 에너지공학
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• 제26권1호
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• pp.54-61
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• 2017

In general, solid waste arises from lots of human activities such as domestic, agricultural, industrial, commercial, waste water treatment, construction, and mining activities etc. If the waste is not properly disposal and treated, it will have a negative impact to the environment, and hygienic conditions in urban areas and pollute the air with greenhouse gases (GHG), ground water, as well as the soil and crops. In this paper, the Carbon Resources Recycling Appropriate Technology Center feasibility studies are reported at Bantayan Island, Philippines on the municipal solid waste management. The present objective of our study is to characterize the municipal solid waste incineration (MSWI) bottom ash and case study of MSWI production status in Bantayan, Philippines. Currently, wide variety of smart technologies available for MSWI management in developed countries. Recycling is the other major alternative process for MSWI landfill issues. In this paper, the feasibility studies of applied appropriate technologies for the municipal solid waste generation in Bantayan Island, Philippines are reported.

• 펄프종이기술
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• 제44권4호
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• pp.8-15
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• 2012

Optical property improvements for ONP (old newspaper) and OMG (old magazine) were attempted by application of in-situ $CaCO_3$ formation process on recycled fiber surfaces. Washing treatment of ONP and OMG resulted in 35~40% yield loss for around 6% brightness improvement. Washing plus bleaching process with $H_2O_2$ and FAS (formamidine sulfinic acid) improved brightness and ERIC values a little more with the same amount of yield loss as washing treatment. In-situ $CaCO_3$ formation method improved those optical properties much better than the washing plus bleaching method without loss of yield, and better than the case of adding high brightness PCC up to the same ash level. It can be said that the in-situ $CaCO_3$ formation method may be used as an effective alternative for upgrading optical properties of recycled fibers.

• International Journal of Computer Science & Network Security
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• 제23권1호
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• pp.17-24
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• 2023

The objective of this paper is to use Geographical Information Systems for identifying Digital Divide in Riyadh Neighborhoods, Saudi Arabia. Geo-database was created that includes Streets, Neighborhoods, ICT Access Data and Coverage Map for Riyadh. We used QGIS and overlay for analysis, intersection selected as tool for this paper. The results indicate that after analyzing the use of information communication technology in all regions of the Kingdom it turns that Riyadh, Ash Sharqiyyah and Makkah in average with percentage 50%, While Al Jawf, Al Madinah, and Najran are the least with percentage 42%. Then we focused on Riyadh to analyze the digital divide because it is the capital of Saudi Arabia and occupations the highest percent of communications towers in the KSA due to population density. Regarding coverage of the 4G, the neighborhoods at the center have recorded very high coverage score. While neighborhoods at the edges of the city have low values of coverage score. Same for 3G, it is more intense in the center and the coverage percentage is higher than 4G. For 2G we found it had the highest coverage compared to 3G or 4G

• 펄프종이기술
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• 제46권4호
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• pp.1-10
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• 2014

In papermaking industry, inorganic fillers are widely used for the purpose of improving opacity, brightness, printability, uniformity and dimensional stability. They are also useful for production costs and energy savings. In the past, inorganic fillers in papermaking industry only focused on micro-scale but recently, new trials on nano-powdered technology are applying. Even nano-powdered fillers are rapidly utilized for improving the optical and surface properties in coating and surface sizing, there still have some problems in wet-end process due to poor dispersibility and retention. In this study, nano-particled calcium carbonate was produced by milling the PCC and its applicability between micro sized and nano sized calcium carbonated was compared in wet-end process, and finally the sheet properties were evaluated. Nano-PCC was not retained in sheet structure without applying retention system, but with retention system nano-powdered PCC was absorbed on fiber surface with expanding the fiber networks. The application of PAM-bentonite system has resulted in high ash retention and bulky structure for copier paper, and good optical properties in brightness and opacity. However, it required to solve the weakness of low tensile property due to interruption of hydrogen bonding by nano fillers.

• 펄프종이기술
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• 제42권2호
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• pp.53-60
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• 2010

Kudzu vine (Pueraria lobata) is a perennial plant and spreads all around in South Korea. Recently the use of leaves, stems and roots of kudzu vine has been investigated in many fields. However, the research on kudzu fibers has not been performed in korean pulp and paper industry. As the stems and roots of kudzu were estimated to contain cellulosic fibers, the possibility of producing a raw material from kudzu fibers in pulp and paper mills was investigated in this study. The stems and roots of kudzu were collected in woods, and then the chemical composition and ash contents was measured. To acquire kudzu pulp, kraft pulping and bleaching of kudzu roots were carried out sequently. After making kudzu pulp, freeness and fiber length were measured, and handsheets was also prepared with kudzu pulp and the properties of handsheets were determined. Consequently, kudzu fibers have lower holocellulose contents than wood fibers and other non-wood fibers. Average fiber length is shorter than that of Sw-BKP, but shows the same level as that of Hw-BKP. The handsheet made from kudzu pulp shows the bulkier structure than those made from Hw-BKP and Sw-BKP.

• 한국화재소방학회논문지
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• 제21권1호
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• pp.90-97
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• 2007

주거공간에 사용되는 벽지의 화재 위험성을 평가하기 위하여 몇 종류의 벽지 시료에 대한 연소특성과 연소가스의 독성을 분석하였다. 본 연구에서 재의 잔량은 고온의 전기로를 이용하여 측정하였으며 TGA를 이용하여 열적 특성을 분석하였다. 연소시간과 연기농도의 측정은 콘히터와 가스분석계를 사용하였고 연기밀도는 ASTM E662의 장치를 이용하였다. 실험결과 실크벽지는 다른 벽지에 비해 낮은 온도에서 열분해가 시작되었는데 이는 실크벽지가 낮은 열유속(heat flux)에서도 착화될 수 있으므로 다른 벽지보다 화재 위험성이 높다. 실크벽지의 복사 열유속에 의한 착화시간은 다른 시료들에 비해 짧아서 화재 시 피난 시간이 짧아져야 하며 비닐이 코팅된 실크벽지 연소 시 일산화탄소의 발생 농도가 가장 높아서 독성의 위험이 높을 것으로 보인다. 실크벽지와 실크방염 벽지의 비닐 코팅으로 연기밀도가 높게 나타났다.