• Computers and Concrete
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• 제20권3호
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• pp.283-290
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• 2017

The aim of this study is to investigate the effect of the bond strength of self-compacting mortars (SCMS) produced from ground pumice powder (GPP) as a mineral additive. In this scope, six series of mortars including control mix were prepared that consist of 7%, 12%, 17%, 22% and 27% of ground pumice powder by weight of cement. A total of 54 specimens of $40{\times}40{\times}160mm$ were produced and cured at the age of 3, 28 and 90-day for compressive and tensile strength tests and 18 specimens of $150{\times}150{\times}150mm$ mortar were prepared and cured at 28 days for bond strength tests. Flexural tensile strength and compressive strength of $40{\times}40{\times}160mm$ specimens were measured at the curing age of 7, 28 and 90-day. Mini V-funnel flow time and mini slump flow diameter tests were also conducted to obtain rheological properties. As a result of the study, it was observed that the SCMs containing 12% of GPP has the highest bond strength as compared to control and GPP mortars. Compressive strength slightly increased up to 12% of GPP.

• Steel and Composite Structures
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• 제23권5호
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• pp.543-555
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• 2017

The mechanical properties of steel fiber reinforced high strength concrete (SFRHSC) made with binary and ternary blends of metakaolin (MK) and ground pumice (GP) are investigated in this study. The investigated properties are ultrasonic pulse velocity ($U_{pv}$), compressive strength ($f_c$), flexural strength ($f_f$) and splitting tensile strength ($f_{st}$) of SFRHSC. A total of 16 steel fiber reinforced concrete mixtures were produced by a total binder content of $500kg/m^3$ for determining the effects of MK and GP on the mechanical properties. The design $f_c$ was acquired from 70 to 100 MPa by using a low water-binder ratio of 0.2. The test results exhibit that high strength concrete can be obtained by replacing the cement with MK and GP. Besides, correlations between these results are executed for comprehending the relationship between mechanical properties of SFRHSC and the strong correlations are observed between these properties. Moreover, two models in the gene expression programming (GEP) for predicting the $f_c$ of SFRHSC made with binary and ternary blends of MK and GP have been developed. The results obtained from these models are compared with the experimental results. These comparisons proved that the results of equations obtained from these models seem to agree with the experimental results.

• 지질학회지
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• 제54권5호
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• pp.513-527
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• 2018

울릉도 말잔등응회암의 화성쇄설층에 대해 입도측정과 구성원 분석을 수행하고 주요 분화유형과 역학적 기구를 해석하였다. 말잔등응회암은 나리 칼데라 외측부에서 3개 멤버로 구분되며, 각 멤버는 하부에 조립 응회암층 및 라필리암층과 상부에 부석층 등의 암상으로 구성된다. 응회암층 및 라필리암층은 순수한 부석층과 구별되는 입도 및 구성원의 정량적 증거를 나타낸다. 응회암층 및 라필리암층은 부석층에 비하여 암편/본질 비와 결정/본질 비의 상대적 증가, 본질 부분의 우세한 파쇄작용 등의 특징을 가진다. 응회암층 및 라필리암층에서 암편과 결정의 풍부성은 지하수의 폭발적 기화로 주인암의 우세 파쇄작용, 체공 중에 세립물질의 제거에 의한 암편 및 결정의 간접적 농집과 같은 이유 때문일 수 있다. 위의 자료는 수증기마그마성 분화가 앞서 일어났고 마그마성 분화가 뒤따라 일어났음을 나타낸다. 즉 응회암층 및 라필리암층은 지하수가 화도로 접근하여 마그마가 물과 폭발적 상호작용에서 유래되는 수증기마그마성 분화(수증기플리니언 분화)를 암시하며, 부석층은 본질 가스압에 의한 마그마성 폭발작용(플리니언 분화)에서 유래되는 화성쇄설물을 나타낸다. 결론적으로 초기에는 마그마 기둥이 낮을 때 정압수가 화도에 접근하여 마그마와 폭발적인 상호작용으로 수증기플리니언 분화를 일으켰으며, 후기에 마그마 기둥의 상승으로 마그마성 가스압이 지하수압보다 커져 화구로의 지하수 접근을 차단함으로서 마그마성 휘발성물질에 의해서만 일어나는 플리니언 분화로 전환되었다.

• Restorative Dentistry and Endodontics
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• 제29권5호
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• pp.454-461
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• 2004

The purpose of this study is to compare and to evaluate the effects of the degree of saturation on the progression of artificial root caries lesion. A total of 8 human premolars without any defects and cracks selected and the cementum were removed and the teeth were cleaned with ultrasonic device and pumice without fluoride. Each tooth was sectioned into 6 pieces and they were ground with #800 sandpaper until they had a thickness of 200pm. Specimens were applied with nail vanish except for the 2-3 mm window area after application of bonding agent. Under the constant pH, the specimens were divided into 6 groups (degree of saturation: 0.1415, 0.1503, 0.1597, 0.1676, 0.1771. 0.1977). Each group was immersed in acid buffer solution for 1. 2, 3, 5 days under controlled temperature ($25^{\circ}C$) and imbibed in water and examined using the polarizing microscope. The results were as follows 1. Although the degree of saturation of demineralization solution decreased, the depth of penetration in the dentin was constant. 2. Erosion was observed on the surface of all the teeth in the group I, II. In the group III, IV, V, surfaces were not changed. The teeth in the group VI showed the more mineralized surface but not the shape of the dentinal tubules distinctively. 3. In all groups, the lesion progressed rapidly at the first day of the experiment, but increased gradually as time elapsed.

• 복식문화연구
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• 제3권2호
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• pp.241-260
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• 1995

The Maori's traditional clothing materials, basic forms of dress, and the pattern and technique of tatoo were examined in the present study in order to deepen the appreciation of the cultural heritage of the Maori. The research method employed was the analysis of written materials. And a fild-trip was also made for the study. The study was limitted to the traditional culture of body adornment of the Maori including the clothing which is preserved and practicing by them at the present day, and the origin and the process of the historical development of those are not included in the scope of the present study. Followings are the results of the study: (1) By far the most widely used fiber for Maori clothing is abtained from what is commonly called New Zealand Flax. The fiber of kiekie(Freycinetia baueriana) and cabbage trees(Cordyline spp.) may also be used. The strong, long-lasting fiber of toi(cordyline indivisa) is used for a prestige warrior's cloak. Flat strips of ti kauka(Cordyline australi) are also used as thatch on rain cloaks. (2) Regardless of technique used, Maori weaving is always worked horizontally from left to right. Traditionally the work was suspended between two upright turuturu or weaving sticks. As the work progressed a second pair of uprights was used to keep the work off the ground. These uprights were moved forward as required. Because the weaver sat on the ground, the working edge was kept at a height that was comfortable to reach. No weaving tools are used, the wefts(aho) being manipulated by the fingers. The two main Maori weaving techniques are whatu aho patahi(single-pair twining) and whatu aho rua(double-pair twining). (3) The Maori wore two basic garments - a waist met and a cloak. The cloth of commoners were of plain manufacture, while those of people of rank were superior, sometimes being decorated with feather or dyed tags and decorated borders. Children ran more-or-less naked until puberty, being dressed only for special events. Some working dress consisted of nothing more than belts with leaves thrust under them. Chiefs and commoners usually went barefoot, using rough sandals on journeys over rough country (4) The adornment of men and women of rank was an important matter of tribal concern as it was in chiefly persons that prestige of the group was centred, The durable items of Maori persons adornment were either worn or carried. Ornaments of various kinds were draped about the neck or suspended from pierced earlobes. Combs decorated the head. Personal decorations not only enhanced the appearance of men and women, but many had protective magical function. The most evident personal ornament was the hei-tiki made of jade or other material. Maori weapons were treasured by their owners. They served on bottle and were also personal regalia. A man of rank was not fully dressed without a weapon in hand. Also weapons were essential to effective oratory. (5) No man or woman of rank went without some tattoo adornment except in extremely rare instances when a person was too sacred to have any blood shed. The untattooed were marked as beeing commoners of no social standing. This indelible mark of rank was begun, with appropriate rite and ritual, at puberty. And tattoo marked the person as being of a marriageable age. Maori tattoo was unlike most traditional tattoo in that its main line were 'engraved' on the face with deep cuts made by miniature bone chisels. The fill-in areas were not tattooed with cuts but with the multiple pricks of small bone 'combs' that only lightly penetrated the skin surface. The instrument of tattoo consisted of small pots of pumice or wood into which was placed a wetted black pigment made from burnt kauri gum, burnt vegetable caterpillars or other sooty materials. A bird bone chisel or comb set at right angles on a short wooden handle was dipped into the gigment, that a rod or stick was used to tap head of this miniature adze, causing penetration of the skin surface. Black pigment lodged under the skin took on a bluish tinge. A full made facial tattoo consisted of major spirals with smaller spirals on each side of the nose and sweeping curved lines radiating out from between the brows over the forehead and from the nose to the chin. The major patterns were cut deep, while the secondary koru patterns were lightly pricked into the skin.