• Fisheries and Aquatic Sciences
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• 제3권1호
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• pp.1-7
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• 2000

Different substrata fixed as the roof (for shadow) on artificial iron reef had been developed as a tool for valuable fishery resources. The experiment was set up on a sandy bottom substratum at 8m depth in Muronohana, Ikata, Japan. Within one month of placement of the plates, diatoms dominated the experimental plates with a coverage of $100\%$ approximately. Enteromorpha intestinalis and Colpomenia sinuosa dominated within three months after the placement. E. intestinalis coverage on substrata was estimated $7\%$ on the plate shaped iron bar, $12-14\%$ on concrete plates, $18\%$ on the plate fixed pebble, $61\%$ on the plate to accumulated wood, and 80-100% on the steel materials plate. Whereas after four months of placement, C. sinuosa coverage on plates became $1-36\%$ on different plates, and $100\%$ on the plate to accumulated wood. The differences in E. intestinalis and C. sinuosa colonization on the different substrata were probably due to variations in their surface roughness influencing the settlement of zoospores, and thus gametophyte. development. After five months of placement, the above two species slowly disappeared.

• 한국해양공학회지
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• 제18권1호
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• pp.53-62
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• 2004

The Purpose of this study is to recycle the waste concrete, which is generated in huge quantities, from construction works. in order to achieve this goal, it is important to determine the compressive strength, workability, slump, and ultrasonic velocity of recycled aggregate concrete. Thus, several experiment parameters are considered, such as water-cement ratios, sand percentage, and fine aggregate composition ratios, in order to apply the recycled aggregate concrete to pre-cast artificial fishing reefs. From the results, it has been shown that the proper mix designs for reef concrete are W/C=45%, S/a=50%, SR50:SN50 in recycled sand and natural sand mix combination case, W/C=45%, S/a=50%, SC50:SN50 in crushed sand and natural sand mix combination case, W/C=45%, S/a=50%, SR50:SC50 in recycled sand and crushd sand mix combination case. Also, this study shows that the shape and surface roughness of fine aggregate particles have an effect on the strength, slump, ultrasonic velocity of tested concrete, and the compressive strength ratios of 7days' and 90days' curing ages of recycled aggregate concrete are about 70% and 110% of 28days' curing age.

• Tribology and Lubricants
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• 제38권4호
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• pp.152-161
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• 2022

Chemical mechanical planarization (CMP) is a technology that planarizes the surfaces of semiconductor devices using chemical reaction and mechanical material removal, and it is an essential process in manufacturing highly integrated semiconductors. In the CMP process, a conditioning process using a diamond conditioner is applied to remove by-products generated during processing and ensure the surface roughness of the CMP pad. In previous studies, prediction of pad wear by CMP conditioning has depended on numerical analysis studies based on mathematical simulation. In this study, using an artificial neural network, the ratio of conditioner coverage to the distance between centers in the conditioning system is input, and the average conditioning density, standard deviation, nonuniformity (NU), and conditioning density distribution are trained as targets. The result of training seems to predict the target data well, although the average conditioning density, standard deviation, and NU in the contact area of wafer and pad and all areas of the pad have some errors. In addition, in the case of NU, the prediction calculated from the training results of the average conditioning density and standard deviation can reduce the error of training compared with the results predicted through training. The results of training on the conditioning density profile generally follow the target data well, confirming that the shape of the conditioning density profile can be predicted.

• 대한치과보철학회지
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• 제37권4호
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• pp.465-473
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• 1999

Bond strength of luting cements to dentin is a critical consideration for success of complete cast crowns. This study was performed to evaluate the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of cemented restorations. Eighty artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a special device on recently extracted human teeth. Coarse diamond(#102R, Shofu) and superfine finishing diamond(#SF102R, Shofu) burs of similar shape were used. Crowns in each group were randomly subdivided into few subgroups of 10 for luting cements selected for this study: zinc phosphate cement (FLECK' S), polycarboxylate cement (Poly-F), rein-forced glass ionomer cement (Fuji PLUS). and adhesive resin cement (Panavia 21). Retention was evaluated by measuring the tensile load required to dislodge the artificial crown from tooth preparations with an Instron testing machine, and analysed by one-way ANOVA and Student's t-test. The obtained results were as follows ; 1. When tooth preparation was done with coarse diamond bur, retentive force was diminished in order of Panavia 21 Fuji PLUS, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Fuji PLUS group and FLECK'S group(p<0.001). 2. When tooth preparation was done with superfine diamond bur, retentive force was diminished in order of Fuji PLUS, Panavia 21, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Panavia 21 group and FLECK'S group(p<0.001). 3. Retentive force in coarse tooth surfaces was significantly higher than that in superfine tooth surface with all luting cements(p<0.001), and cement residues were almost retained with-in the cast crown in all groups.

• Journal of Biosystems Engineering
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• 제21권4호
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• pp.429-435
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• 1996

A wind tunnel consisting of two air flow conditioners with polycarbonate pipes, a plant growth room, a suction fan and fan controller, and fluorescent lamps, was designed to investigate the interactions between the growth of plug seedlings under artificial light and their Physical environments. Light transmissivities in the plant growth room based on the photosynthetic photon flux density and photosynthetically active radiation was appeared to be 96.3% and 96.8%, respectively. Measurement showed a uniformity in the vertical profiles of air current speed at the middle and rear regions of plug trays in wind tunnel. This result indicated that the development of a wind tunnel based on the design criteria of the American Society of Mechanical Engineers was adequate. Air current speed inside the plug stand was significantly decreased due to the resistance by the leaves of plug seedlings and boundary layer developed over and below the plug stand. Driving force to facilitate the diffusion of gas inside the plug stand might be regarded as extremely low. Aerodynamic characteristics above the plug stand under artificial light were investigated. As the air current speed increased, zero plane displacement decreased but roughness length and frictional velocity increased. Zero plane displacement linearly increased with the average height of plug seedlings. The wind tunnel developed in this study would be useful to investigate the effects of air current speed on the microclimate over and inside the plug stand and to collect basic data for a large-scale plug production under artificial light in a semi-closed ecosystem.

• 한국안광학회지
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• 제10권2호
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• pp.119-126
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• 2005

2개사 칼라콘택트렌즈에 대한 물성적 특성을 평가 비교하였다. 제조된 인공누액을 사용하여 단백질 침착율과 습윤성, 주사전자현미경과 원자간력현미경을 이용하여 렌즈의 표면 거칠기를 관찰하였다. 결과는 다른 특성들은 일반 소프트콘택트렌즈와 비교해서 큰 차이를 보이지 않았으나 주사전자현미경적 관찰에서 건조시 심한 균열을 보였다. 원자간력현미경적 관찰에서 렌즈 표면요철은 발견되지 않아 표면거칠기는 일반 소프트콘택트렌즈와 차이가 없었다. 렌즈 앞면과 뒷면에 대한 염료 침착을 확인한 결과 염료는 렌즈내부에 존재함을 알 수 있었다.

• 한국전기전자재료학회논문지
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• 제20권10호
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• pp.839-845
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• 2007

In this paper, a polishing pad has been analyzed in detail, to understand surface phenomena of polishing process. The polishing pad plays a key role in polishing process and is one of the important layer in polishing process, because it is a reaction layer of polishing[1]. Pad surface physical property is also ruled by pad profile. The profile and roughness of pad is controlled by different types of conditioning tool. Conditioning tool add mechanical force to pad, and make some roughness and profile. Formed pad surface will affect on polishing performance such as RR (Removal Rate) and uniformity in CMP Pad surface condition is changed by conditioning tool and dummy run and is stable at final. And this research, we want to reduce break-in and dummy polishing process by analysis of pad surface and artificial machining to make stable pad surface. The surface treatment or machining enables to control the surface of polishing pad. Therefore, this research intends to verify the effect of the buffing process on pad surface through analysis of the removal rate, friction force and temperature. In this research, urethane polishing pad which is named IC pad(Nitta-Haas Inc.) and has micro pore structure, is studied because, this type of pad is most conventional type.

• 한국전기전자재료학회논문지
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• 제20권12호
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• pp.1027-1033
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• 2007

In this research, the polishing pad for W CMP has been analyzed to understand stabilization of polishing performance. For stabilization of process, the polishing pad condition is one of important factors. The polishing pad plays a key role in polishing process, because it contact with reacted surface of wafer[1]. The physical property of pad surface is ruled by conditioning tool which makes roughness and profile of pad surface. Pad surface affects on polishing performance such as RR(Removal Rate) and uniformity in CMP. The stabilized pad surface has stable roughness. And its surface has high level of wettability which can increase the probability of abrasive adhesion on pad. The result of this research is that the reduction of break-in and dummy polishing process were achieved by artificial machining to make stable pad surface. In this research, urethane polishing pad which is named IC pad(Nitta-Haas Inc.) and has micro pore structure, is studied. Because, this type of pad is the most conventional type.

• 한국지형학회지
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• 제27권1호
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• pp.21-31
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• 2020

Planting pine trees on the coastal dunes has been carried out along the East coast as well as West coast of South Korea. Although the artificial forestation has been regarded as a good policy that help to protect the coastal area from natural disasters, but its real effect to the landscapes is still unknown. In this study, we have installed a monitoring site with an automated weather station to study requirements for dune formation and its environmental changes in Osan beach, Yangyang-Gun, Gangwon Province. We analyzed the meteorological data collected from 2010 to 2019 and vegetational changes in the study area. As a result, the wind speed is decreased by around 30% and the pine-covered area is increased by around 300m² after planting Japanese Black Pine in 2015. At present, it seems that the eolian transport of sand particle is minimal, because the dominant winds are the westerly winds which is not landward but seaward, and because the surface roughness length is about 0.5m which is similar to that in the deciduous forest.

• 터널과지하공간
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• 제9권4호
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• pp.350-363
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• 1999

주기전단하중 하의 암석 절리에 대한 역학적 거동을 규명하기 위해 정밀 주기전단시험 장치를 설계·제작하였다. 실험실에서 황등화강암과 여산대리석 인공 절리 시료로 펑면절리와 거친 절리에 대해 일련의 주기전단시험을 실시하였다. 시료에 대한 레이저 변위계를 이용한 3차원 거칠기 측정을통해 절리의 거칠기 특성을규명하였다. 주기전단시험 결과를 통해 주기전단 과정의 단계별 거동 특성과하중과제하시의 거동 차이, 전단거동의 이방성 등을고찰하였다. 거친 절리면의 역학적 거동 특성은 주로 2차 거칠기의 영향과 암석 재료의 높은 강도에 영향을 받았다. 주기전단시 거친 절리에 대한 돌출부 손상이 지수적인 거칢각 손상 법칙을 따름을 실험적으로 검증하였으며, 수직응력파 거칠기 종류, 하중 단계에 따라 돌출부들의 손상 기구가 다름을 확인하였다.