• 지질공학
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• 제26권4호
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• pp.439-445
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• 2016

신축되는 공항은 미래 항공수요를 선점하고 주변지역 공항들과의 경쟁에서 앞서나가기 위해, 고품질의 활주로를 건설하고자 체계적으로 활주로 하부지반 건설에 임하고 있다. 본 연구에서는 여객계류장 운영시 하부 연약지반의 잔류침하를 최소화 할 수 있도록 시공관리하기 위하여 기존의 표준다짐시험의 단점을 보완하는 연구를 하고자 하였으며, 직경 100 mm 이하의 성토 재료를 사용한 4개소 현장에서 성토재료를 채취하여 표준다짐시험(KS F 2312), 대형원형몰드 다짐시험, 물치환 현장밀도시험(ASTM D 5030)을 수행하였다. 현장밀도시험과 표준 실내다짐시험의 상관관계를 회귀분석 하면, 유의수준(P-value) 0.05에서 신뢰할 수 없는 값을 나타내었으며, 현장밀도시험과 대형 실내다짐시험의 회귀분석 결과 상관계수(R)가 0.8878로 상관관계가 높게 나타났다. 설계 및 시공에 사용되는 최대건조밀도를 평가할 때 성토재료의 최대치수를 고려하여 다짐시험방법이 선택되어야만 현장여건이 충실히 반영되어 전체적으로 균질한 품질의 시공이 이루어 질 수 있을 것으로 판단된다.

• 한국농공학회지
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• 제36권4호
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• pp.103-116
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• 1994

The objective of this study was to determine the criteria for density and moisture content measurements made with a nuclear density meter on common materials in the construction field. The study also sought to test a full-type nuclear density meter in controlling the density of overlay layers( 2.5~5.0cm). In order to determine the accuracy and reliablility of nuclear guage measurements made on construction materials, laboratory and field tests were conducted. Wooden blocks( 65 x 45 ${\times}$ 50 cm) and a special steel compactor( 4.7kg) were constructed in order to carry out tests which were conducted on three different materials; coarse gramed soil, fine grained soil, and AC material. Throughout all laboratory and field tests, the nuclear density and moisture content were determined using Humboldt 5OOLP nuclear gauge. The tests on subgrade material entailed obtaining density measurements by means of both the sand replacement method and the nuclear density meter. The results of the sand replacement method were then compared to the readings recorded bu the meter. As in the subgrade material tests, density measurements made during AC pavement tests were also determined using the unclear meter in addition to a second means; through the core method. The meter readings and core densties were compared as was done in the tests on subgrade materials. The correlation between the results of the sand replacement test( also, the core method) and meter readings on subgrade material was then determined. Sirnilarly, the observed results were then analyzed through linear regression. The tests to determine thin-lift density by means of a full-type nuclear density meter also conducted on the overlay layers( about 4. 8cm thickness) above AC pavements at road construction sities in Korea.

• 한국광학회:학술대회논문집
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• 한국광학회 2000년도 제11회 정기총회 및 00년 동계학술발표회 논문집
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• pp.168-169
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• 2000

We have tried to enhance the density of the near-field optical memory and to improve the recording/readout speed. The current optical memory has the limitation in both density and speed. This barrier due to the far-field nature can be overcome by the use of the near-field$^{(1)}$ . The optical data storage density can be increased by reducing the size of the nanometric aperture where the near-field is obtained. To fabricate the aperture in precise dimension, we applied the orientation-dependent / anisotropic etching property of crystal Si often employed in the field of MEMS$^{(2)}$ . And so we fabricated the 10$\times$10 aperture array. This array will be also the indispensable part for speeding up. One will see the possibility of the multi-tracking pickup in the phase changing type memory through this array$^{(3)}$ . This aperture array will be expected to write the bit-mark whose size is about 100nm. We will show the recent result obtained. (omitted)

• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.385-390
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• 1999

In this paper, we investigated the wear rate, braking temperature and stopping distance of the composite brake shoe for diesel locomotive in the field test. The wear rate and braking temperature of the composite brake shoe would rather than cast iron. Also, the stopping distance of composite brake shoe is 450m at 100km/h. This result of field test shown that the density distribution of the composite brake shoe influence on wear rate.

• 한국도로학회논문집
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• 제18권6호
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• pp.87-96
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• 2016

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between different sizes of variable speed limit signs and the legibility distance under various fog density conditions. By using this study, appropriate sizes of signs can be selected depending on the density of fog. METHODS : An actual tunnel was selected as the area for this test, as other places cannot maintain the fog condition because of rapid air current. A total 121 subjects were recruited for this test, which took place over the course of four days. The test on the first day was conducted under normal weather conditions for comparison. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS : The test results show the relationship between the different sizes of signs and the legibility distance corresponding to the visibility distance due to both non-fog and fog generated conditions. According to the technical test results, appreciable amount of reduction in legibility distance due to fog was resulted in all sizes of signs. Moreover, the legibility distance is reduced proportionately with the decrease in the visibility distance due to fog. CONCLUSIONS : The results of this study can be used to select appropriate sizes of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

• 한국도로학회논문집
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• 제18권6호
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• pp.77-85
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• 2016

OBJECTIVES : A fog generated field test was conducted to analyze the relationship between the luminance of variable speed-limit signs and the legibility distance under various fog density conditions. By using this study, appropriate luminance values can be selected depending on the density of fog. METHODS : An actual tunnel was selected as the area to conduct the test, as other places cannot maintain the fog condition because of rapid air current. Ninety-two subjects were recruited for this test, which took place during the course of three days. Visibility-distance detecting sensor was used to measure the visibility distance due to the fog density time, simultaneously with the evaluation of legibility distance by subjects. RESULTS : The test results show the relationship between luminance values and the legibility distance corresponding to the visibility distance due to fog. According to the technical test results, lower luminance value such as $7000cd/m^2$ corresponds to less legibility distance compared to higher values such as $20000cd/m^2$ or $40000cd/m^2$. However, the amount of difference between $20000cd/m^2$ and $40000cd/m^2$ is negligible in our test. CONCLUSIONS : The results of this study can be used to select appropriate luminance of valuable speed signs under fog conditions. Hence, drivers can expect to have more room to respond to adverse weather conditions, thereby reducing the risk of accidents.

• 한국도로학회논문집
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• 제8권3호
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• pp.115-127
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• 2006

현재 중부내륙 고속도로 시험도로(test road)에는 환경하중에 대한 도로 포장체의 환경적인 거동 특성을 파악하기 위하여 다져진 노상토에 WCR형태의 함수량계로 측정되는 체적 함수량이 현장 밀도의 영향등으로 부정확하게 예측되는 경향을 나타내고 있다. 따라서 본 연구에서는 흙의 특성과 현장 밀도를 고려하여 현장에 적합한 함수량 보정을 실내 및 현장시험을 각각 실시하고 이를 토대로 보정방정식을 제안하였다. 연구 결과 보정된 함수량은 현장의 측정치에 근접하게 판명되었다. 따라서 WCR을 활용하여 다짐된 노상토 지반의 체적 함수량을 측정시 사용된 흙의 종류 및 다짐조건 등이 고려되어야 한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1994년도 가을 학술발표회 논문집
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• pp.265-272
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• 1994

The relative density seems to be important as a factor of controlling the physical properties in the case of cohesionless soil ground as sand. Therefore, the study is more important about the method for reappearing the same relative density when the specimen of shearing test is to be produced or the model test of ground is to be made. In this study, the apparatus making use of the multiple sieving pluviation method - one of the reappearance of relative density - could be made. Using this apparatus, tests were practiced varying the factors such as the size of sieve mesh and the number of sieve, the amount of falling discharge, the falling height etc. about the standard sand in Jumunjin and Hadong sand. When laboratory test is performed by the cohensionless soil , it presents the method for reappearing of the relative density in field.

• 한국농공학회논문집
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• 제60권6호
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• pp.111-119
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• 2018

The air-void is known to be one of the influencing factors for estimating long-term performance of asphalt concrete. Most of all, confirming air void or density of pavement layer is important for quality control of field compaction level of asphalt concrete pavement. In this study, a non-nuclear type non-destructive density gage (NDDG) was used to estimate compacted air-voids of asphalt pavement as a non-destructive test method. Asphalt concrete slab specimens were prepared using 6 types of asphalt mixes in laboratory (lab) for lab NDDG test. Four different base structure materials were used to find out if there were any differences due to the type of base structure materials. The actual air-voids and NDDG air-voids were measured from 6 asphalt concrete slabs. Four sections of field asphalt pavements were tested using the NDDG, and actual air voids were also measured from field cores taken from the site where the NDDG air-void was measured. From lab and field experimental tests, it was found that the air-voids obtained by NDDG were not the same as the actual air-voids measured from the asphalt concrete specimen. However, it was possible to estimate air voids based on the relationship obtained from regression analysis between actual and NDDG air voids. The predicted air-voids based on the NDDG air-voids obtained from 50mm depth were found to be reliable levels with $R^2{\fallingdotseq}0.9$. Therefore, it was concluded that the air-voids obtained from NDDG could be used to estimate actual air-voids in the field asphalt pavement with a relatively high coefficient of determination.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.102-105
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• 2006

Forest canopy density is an essentially important for maintaining the diversify flora and fauna in the tropic. But, the natural and human disturbances have an influence over the inconsistency of forest canopy density. So, forest canopy density (FCD) has been threatened in the tropic since a decade. The objective of this study was to examine the dynamics change of the forest canopy density in tropical forest Chitwan, Nepal combine with field survey and remote sensing data. The field survey data of 2001 such as canopy cover percentage, dbh so on and some human disturbances were used. Similarly, Landsat TM 1988 and ETM+ 2001 have also used to predict the dynamic changes of the FCD over the period. Moreover, nonparametric Kruskal- Wallis test has performed for the validation of the results. Data analysis revealed that very few factors i.e. the number of trees, path, and fire had realized statistically significance at P=<0.05. Therefore we concluded that detail analysis could be needed incorporate with additional socioeconomic, climatic, biophysical and institutional factors for the better understanding of the forest canopy dynamic in particular location.