• 정보저장시스템학회논문집
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• 제2권3호
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• pp.184-188
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• 2006

In recent years the flying height of the head/slider has been decreasing in order to increase the recording density of hard disk drive (HDD). Accordingly, it was predicted that direct contact between slider and disk surface (slider slap) can cause defects on the disk such as scratch and particle generation. In this work, we theoretically demonstrate the effect of rounded-edge slider using Hertzian contact theory. Depth and width of scratch were predicted by plowing model. Furthermore, as we fabricated rounded-edge slider, rounded-edge slider was tested and compared with sharp-edge slider. The experimental results show rounded-edge was effective for reducing scratch depth.

• 대한기계학회논문집
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• 제18권10호
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• pp.2597-2605
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• 1994

The wear behavior of two types of $Si_3N_4$ exposed to high and low humidity was examined at various sliding speeds, using bearing steel as disk material under pin-on-disk type sliding conditions. Higher wear rates were obtained at a high humidity than at a low humidity. As the sliding speed was increased, the wear rates were decreased and the effect of humidity on the wear rates of $Si_3N_4$ was reduced. The result that the $Si_3N_4$ pin showed higher wear rate under the high humidity condition was explained by the decrease in microhardness of $Si_3N_4$ due to the chemisorbed moisture on the pin and plowing action by the hard particles of $Fe_2O_3$ from the disk. An increase in the sliding speed is supposed to reduce the effect of humidity on the wear rate of $Si_3N_4$ by raising the average temperature of the disk surface and the local temperature at pin-disk contact point.

• 한국토양비료학회지
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• 제32권3호
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• pp.254-260
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• 1999

본 연구(硏究)는 호남평야지(湖南平野池) 논토양(土壤)의 대표토양(代表土壤)인 전북통(全北統)에서 벼 무논골뿌림직파물리성개선(直播物理性改善) 및 진단시비(診斷施肥)에 의한 쌀 안정(安定) 증수방법(增收方法)을 구명(究明)하고자 관행(慣行), 진단시비(診斷施肥), 진단시비(診斷施肥)+심경(深耕), 심토파쇄(心土破碎), 진단시비(診斷施肥)(LCU80%) + 심토파쇄(深土破碎), 무질소구(無窒素區) 등(等) 6처리(處理)로 하여 2년간(年間)('97~'98)에 걸쳐 검토(檢討)한 시험결과(試驗結果)를 요약(要約)하면 다음과 같다. 심경(深耕) 및 심토파쇄시(心土破碎時) 관행(慣行)에 비하여 경도(硬度), 용적밀도(容積密度)가 낮아지고 공극률(孔隙率)이 증가(增加)하여 물리성(物理性) 개선효과(改善效果)가 현저하였으며 화학성분중(化學成分中) 유기물(有機物), 인산(燐酸), 가리함량(加里含量)이 크게 증가(增加)하였다. 시비질소(施肥窒素)의 토양중(土壤中) $NH_4-N$ 용출량(溶出量)은 관행대비(慣行對比) 진단시비(診斷施肥) + 사양물리성개선구(士壤物理性改善區)에서 크게 증가(增加)하였으며, 시비질소(施肥窒素)의 흡수량(吸收量)과 이용률(利用率)은 진단시비(診斷施肥)(LCU80% 전량기비(全量基肥))+심토파쇄구(心土破碎區)에서 가장 많았으며 엽색(葉色)과 경엽중(莖葉中) 질소농도(窒素濃度)는 관행(慣行)에 비하여 진단시비(診斷施肥)+토양특리성개선구(土壤特理性改善區)에서 최고분벽기(最高分蘗期)부터 출수기(出穗期)기까지 높았으며 이들 상호간(相互間)의 유의성(有意性)이 인정(認定)되었다. 쌀수량(收量)은 관행(慣行)보다 진단시비(診斷施肥) 6%, 진단시비(診斷施肥) + 심경구(深耕區) 18%가 증수(增收)하였으나 진단시비(診斷施肥)(LCU80% 전량기비(全量基肥))+심토파쇄구(心土破碎區)에서 23%가 증수(增收)되었고 시비효율(施肥效率)도 가장 높았다.

• 한국약용작물학회지
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• 제16권2호
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• pp.69-73
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• 2008

넓은잎큰조롱의 경운깊이에 따른 생산성 및 품질향상을 위한 구명하기 위하여 경운깊이를 달리하여 2005년부터 2년간 시험한 결과, 만장은 경운깊이가 얕을수록 길어 경운깊이가 30 cm 일 때 685 cm 인데 비하여 경운깊이 10 cm 일 때 59 cm 가 더 길었으며, 경태와 건물중도 같은 경향으로 굵거나 무거웠다. 엽장, 엽폭, 엽중은 경운깊이가 얕을수록 양적인 생육을 보였으나, 엽록소 함량은 경운깊이가 깊을수록 증가하였다. 근수와 근장은 경운깊이가 깊을수록 많거나 길어지는 경향이었으나, 근태와 부패근은 경운깊이가 얕을수록 굵거나 많은 경향이었고, 근수량은 경운깊이가 깊을수록 많은 경향으로 경운깊이가 10 cm 일 때 $622\;kg/1000m^2$인데 비하여 20 cm 이상으로 경운할 때 $7{\sim}9%$ 증수되었다.

• Tribology and Lubricants
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• 제21권5호
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• pp.209-215
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• 2005

Nano/micro friction with the contact area was studied on Si-wafer (100) and diamond-like carbon (DLC) film. Borosilicate balls of radii $0.32{\mu}m,\;0.5{\mu}m,\;1.25{\mu}m\;and\;2.5{\mu}m$ mounted on the top of AFM tip (NPS) were used for nano-scale contact and Soda Lime glass balls of radii 0.25mm, 0.5mm, 1mm were used for micro-scale contact. At nano-scale, the friction between ball and surface was measured with the applied normal load using an atomic force microscope (AFM), and at micro scale it was measured using ball-on flat type micro-tribotester. All the experiments were conducted at controlled conditions of temperature $(24\pm1^{\circ}C)$ and humidity $(45\pm5\%)$. Friction was measured as a function of applied normal load in the range of 0-160nN at nano scale and in the range of $1000{\mu}N,\; 1500{\mu}N,\;3000{\mu}N\;and\;4800{\mu}N$ at micro scale. Results showed that the friction at nano scale increased with the applied normal load and ball size for both kinds of samples. Similar behavior of friction with the applied normal load and ball size was observed for Si-wafer at micro scale. However, for DLC friction decreased with the ball size. This difference of in behavior of friction in DLC nano- and microscale was attribute to the difference in the operating mechanisms. The evidence of the operating mechanisms at micro-scale were observed using scanning electron microscope (SEM). At micro-scale, solid-solid adhesion was dominant in Silicon-wafer, while plowing in DLC. Contrary to the nano scale that shows almost a wear-less situation, wear was prominent at micro-scale. At nano- and micro-scale, effect of contact area on the friction was discussed with the different applied normal load and ball size.

• 한국환경농학회지
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• 제33권2호
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• pp.144-147
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• 2014

BACKGROUND: It is essential to prioritize the exact and clear understanding of agricultural nonpoint source pollution (NPS) controls. The realistic policies and systems should also be developed based on this understanding. Therefore, this study aimed to present agricultural Best Management Practices (BMPs) applicable for the fields based on the Delphi survey result. METHODS AND RESULTS: This study deduced the evaluation items to assess each BMP for agricultural NPS control and conducted the surveying using the Delphi method based on agricultural BMP experts. In addition, its on-the-spot application were evaluated. Considering its importance, technical, social and economic proprieties showed that political support was ranked first and followed by cost investment, labor investment, reduction effect and resident participation. The survey findings by agricultural BMP experts showed the good performance of on-the-spot application can be achieved from fertilization by soil testing, residue and green manure application and contour plowing which are applicable within a field. Agricultural BMPs, highly applicable for the fields, were the countermeasures that farmers who are the principal bodies of agricultural NPS control could be participated directly. CONCLUSION: The active participation of farmers is essential for effective control of agricultural NPS. It is necessary to establish various incentive systems.

• Journal of Radiation Protection and Research
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• 제40권4호
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• pp.231-243
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• 2015

Four different paddy soils collected around the Gyeongju nuclear site were treated with $^{99}TcO_4{^-}$ solution under the assumption of two contrasting contamination scenarios. Scenario I (SN-I) is for a pre-transplanting deposition of $^{99}Tc$ followed by plowing, whereas SN-II is for its deposition onto the water surface shortly after transplanting. Rice plants were grown in lysimeters in a greenhouse. Plant uptake of $^{99}Tc$ was quantified with the $TF_{area}$ ($m^2{\cdot}kg^{-1}-dry$). The SN-II $TF_{area}$ values for straws and brown rice, having been generally higher than the SN-I values, were within the ranges of $6.9{\times}10^{-3}{\sim}4.1{\times}10^{-2}$ and $5.2{\times}10^{-6}{\sim}7.3{\times}10^{-5}$, respectively. Sorption onto clay seems to have decreased $^{99}Tc$ uptake in SN-I, whereas it may have had an insignificant effect in SN-II. A phenomenon characteristic of submerged paddy soil, i.e., the development of a thin oxic surface layer may have greatly affected the rice uptake of SN-II $^{99}Tc$. The surface-water concentrations of $^{99}Tc$ were much higher in SN-II than in SN-I. For the percolating water, however, the opposite was generally true. At most 1.3% of the applied $^{99}Tc$ were leached through such percolation. The use of empirical deposition time-dependent $TF_{area}$ values was considered desirable in assessing the radiological impact of a growing-season deposition of $^{99}Tc$ onto paddy fields.

• 한국환경과학회지
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• 제21권2호
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• pp.181-188
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• 2012

Salicornia europaea (glasswort) is succulent, annual, halophytic plant mainly distributed throughout reclaimed land or salt marsh. It has strong tolerance to salt so that it plays the part of the pioneer species in the first succession. According to domestic and foreign studies, S. europaea contains plenty of minerals and antioxidant in the body. Since people take note of an availableness of this plant as health diet, the natural growth sites are threatened. In addition to development of salt marsh and sea shore, imprudent harvest has a bad effect to S. europaea population maintenance. To seek ways to preserve the population of this plant, we carried out the continuity of seed germination and restoration test. Seokmo Island, Daebu Island, Youngjong Island and Sudokwon landfill in Korea are selected sites for research. Result of germination continuity shows that most S. europaea seeds germinate on March but no more after July. However the germination was occurred after that time in the greenhouse. So we concluded that no germination after July is a matter of environmental condition not the number of remaining seeds. Also germination was seldom occurred in the spot where seeds production was not happened. In result of continuity test of seed germination by soil depth, germination was occurred vigorously only in top soil. From these results, we note that most S. europaea germinate in the early spring, and germination is finished by July. And this rapid germination speed makes the number of seeds in soil seed bank rare. If a large number of S. europaea in some area are harvested after July, the number of this species will dramatically decrease in that area the following year. In Seokmo Island, we carried out reintroduction experiment by sowing S. europaea seeds. On the first year, a small number of S. europaea settled and they produced seeds successfully. On April 2010, the second year, we observed many S. europaea in seed sowing sites. And we found out that plowing is more efficient than treatment sea water for settlement of S. europaea.

• 한국환경농학회지
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• 제42권1호
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• pp.44-51
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• 2023

Nitrogen fertilizer is an essential macronutrient that requires repeated input for crop cultivation. Excessive use of nitrogen fertilizers can adversely affect the environment by discharging NH₃, NO, and N₂O into the air and leaching into surrounding water systems through rainfall runoff. Therefore, it is necessary to develop a technology that reduces the amount of nitrogen fertilizer used without compromising crop yields. Fertilizer deep placement could be a technology employed to increase the efficiency of nitrogen fertilizer use. In this study, a deep fertilization device that can be coupled to a tractor and used to inject fertilizer into the soil was developed. The deep fertilization device consisted of a tractor attachment part, fertilizer amount control and supply part, and an underground fertilizer input part. The fertilization depth was designed to be adjustable from the soil surface down to a depth of 40 cm in the soil. This device injected fertilizer at a speed of 2,000 m²/hr to a depth of 25 to 30 cm through an underground fertilizer injection pipe while being attached to and towed by a 62-horsepower agricultural tractor. Furthermore, it had no difficulty in employing various fertilizers currently utilized in agricultural fields, and it operated well. It could also perform fertilization and plowing work, thereby further simplifying agricultural labor. In this study, a newly developed device was used to investigate the effects of deep fertilizer placement (FDP) compared to those with urea surface broadcasting, in terms of rice and soybean grain yields. FDP increased the number of rice grains, resulting in an average improvement of 9% in rice yields across three regions. It also increased the number of soybean pods, resulting in an average increase of 23% in soybean yields across the three regions. The results of this study suggest that the newly developed deep fertilization device can efficiently and rapidly inject fertilizer into the soil at depths of 25 to 30 cm. This fertilizer deep placement strategy will be an effective fertilizer application method used to increase rice and soybean yields, in addition to reducing nitrogen fertilizer use, under conventional rice and soybean cultivation conditions.

• 한국농공학회지
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• 제13권1호
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• pp.2162-2176
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• 1971

옛날부터 우리들의 선조들이 한반도에 정착하면서부터 산야를 파서 농경지를 조성하였으며 지력(地力)을 회복하는 대신 토지를 교체하면서 오랫동안 봉건적 농업을 이루어 나왔다. 근대농업은 기계를 도입하였으며 따라서 농지조성도 기계개간을 하게 되었다. 종래와 같이 산지를 파면 된다는 피상적인 형식에 그칠 것이 아니라 실질적으로 개간작업방식, 작업시간, 작업능율, 작물재배효과 등을 종합하여 가장 우수한 방법을 추출(抽出) 연구하여 제3차 경제개발 5개년 계획기간 ($1972{\sim}1976$)에 21만정보의 농경지를 조성하므로서 조국의 근대화에 이바지하고져 기계개간의 새로운 작업체계와 숙지화촉진에 관한 연구를 하게되어 다음과 같은 사실들을 알게 되었다. (1) 토지경사도 $10^{\circ}$정도는 계단전개간보다 원지형개간을 하는 것이 개간작업이나 영농작업에 유리하다. (2) 개간작업에서 잡초를 태우거나 청소하지 않고 가급적 표토에 혼입함으로서 유기물을 공급하고 토양을 팽연하게 하였다. (3) 개간작업은 불도우저, 트랙터, 해로우 자동경운기, 로오타리 틸러등 여러 가지 장비를 갖추어야 일관성있는 작업을 할 수 있다. (4) 발근작업은 나무뿌리가 땅속에 뻗어있는 모양에 관계가 있는 것으로 직근계, 측근계, 사근계 중 직근계가 뽑기 어려웠다. (5) 주름잡이구(IV)의 개간작업이 발근과 첫갈이가 확실하며 쇠토작업도 간단히 처리되었다. (6) 운토량은 $240m^3/10a$로 표준구보다 15.6%정도 증가하였으나 개간작업시간은 2시15분45초/10a로 표준구의 1/3정도 걸렸다. 즉 2/3나 단축되었다. (7) 디스크 해로우잉(쇠토작업)은 기경지(旣耕地)쇠토작업에 비하여 작업시간이 50%증가하여 15분/10a 걸렸다. (8) 토오타리 틸링은 작업시간이 기경지에 비하여 2.4배나 증가하여 1시47분43초/10a이었다. 그 까닭은 심토(心土)의 쇠토작업이 어려웠기 때문이다. (9) 개간지는 토성에 맞추어 비료를 투입하여야 한다. 특히 퇴비는 1,200kg/10a. 석회는 20kg/10a 이상 투입할 것이다. 그리고 퇴비생산을 위하여 앞으로 채초지(採草地)가 필요하게 되었다. (10) 목초재배시험은 현재 재배중이어서 아직 그 결과를 알 수 없으나 개간효과와 숙지화정도가 밝혀질 것으로 기대된다.