• 로봇학회논문지
• /
• 제3권1호
• /
• pp.33-41
• /
• 2008

Based on object recognition technology, we present a new global localization method for robot navigation. For doing this, we model any indoor environment using the following visual cues with a stereo camera; view-based image features for object recognition and those 3D positions for object pose estimation. Also, we use the depth information at the horizontal centerline in image where optical axis passes through, which is similar to the data of the 2D laser range finder. Therefore, we can build a hybrid local node for a topological map that is composed of an indoor environment metric map and an object location map. Based on such modeling, we suggest a coarse-to-fine strategy for estimating the global localization of a mobile robot. The coarse pose is obtained by means of object recognition and SVD based least-squares fitting, and then its refined pose is estimated with a particle filtering algorithm. With real experiments, we show that the proposed method can be an effective vision- based global localization algorithm.

• 한국대기환경학회지
• /
• 제15권5호
• /
• pp.677-685
• /
• 1999

Aerosol mass size distributions were measured at Kosan, Cheju Island in April 1998 and their compositions were analyzed. Microorifice Uniform Deposit Impactor(MOUDI) was used to collect aerosols. Sulfate and ammonium ions were predominatly present at fine mode of the aerosols while nitrate, chloride, and metal ions were mostly at coarse mode. Based on the size distribution of nitrate, it is suggested that most nitrate were from gas to particle conversion on coarse particles. Non-sea salt(nss) fraction of sulfate accounted for more than 90% of total sulfate mass concentration. In general, ion concentrations in this study are lower than those measured at the same site from the previous studies. Ion balance and chloride ion levels indicates that there had been anthropogenic chloride emission sources near to the site during the measurements.

• Geomechanics and Engineering
• /
• 제20권2호
• /
• pp.121-129
• /
• 2020

In the design of geotechnical structures, engineers choose either peak or critical state friction angles. Unfortunately, this selection is based on engineer's preference for economy or safety and lacks the assessment of the expected level of deformation. To fill this gap in the design process, this study proposes a strain based empirical method. Proposed method is founded on the experimentally supported assumption that higher dilatancy angles result in more brittle soil response. Using numerous triaxial test data on ten different soils, an empirical design chart is developed that allows the estimation of shear strain at failure based on soil's peak dilatancy angle and mean grain diameter. Developed empirical chart is verified by conducting a small scale retaining wall physical model test. Finally, a design methodology is proposed that makes the selection of design friction angle in structured way possible based on the serviceability limits of the proposed structure.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 1984년도 제26회 수공학연구발표회논문초록집
• /
• pp.7-21
• /
• 1984

Entrainment and deposition experiments were counducted in fresh water on four groups of sediments: three well-defined sediments of uniform composition and narrow-size distribution (1 to 9 um, 10 to 50 um, and 50 to 90 um), and a fourth group which was a mixture of these three sediments. In the entrainment experiments and at a particular stress, the steady-state suspended sediment concentration of the coarse group was the lowest while the concentrations of the fine and medium groups were higher that that of the coarse group but were similar to each other. Deposition experiments generally showed an exponential decrease of suspended sediment concentration with time with the decay time being a function of particle size and applied stress.

• 한국식품영양과학회지
• /
• 제39권6호
• /
• pp.837-842
• /
• 2010

우리밀 semolina의 면류가공 산업현장에 적용될 수 있는 방안을 모색하고자 제분과정 중 발생하는 coarse semolina (CS), medium semolina(MS), fine semolina(FS)의 이화학적 특성을 비교 분석하였다. 실험에 사용한 semolina 모두가 FS를 제외하고는 $250{\mu}m$ 이상의 큰 입자가 약 75% 이상을 차지하였고, MS의 경우 durum semolina(DS)와 가장 유사한 입도분포를 나타내었다. 조단백, 조회분은 DS가 유의적으로 높게 나타났고, 우리밀 semolina는 CS, MS, FS 순으로 감소하였다. 조지방은 DS가 가장 낮게 나타났고, CS, MS, FS는 유의적 차이를 나타내지 않았다. L값은 작은 입도분포를 많이 가질수록 높게 나타났고, 손상전분은 DS와 FS에서 낮게 나타났으며, CS에서 가장 높은 손상전분을 나타내었다. 아밀로오스 함량 또한 비교적 작은 입도분포를 가지는 DS와 FS에서 각각 29.80%과 29.08%로 높게 나타났으며, 물결합력은 DS가 가장 높았고, 우리밀 semolina의 경우 FS에서 높게 나타났다. 용해도와 팽윤력에서도 낮은 손상전분과 작은 입도분포를 가지는 FS에서 높게 나타났다. 미세구조 관찰시 FS와 MS에서 가루로부터 깨끗하고 뚜렷한 작은 전분입자가 파열되지 않고 전분 입자형태를 유지하면서 가루 표면에서 떨어져 나와 있는 전분립들을 관찰할 수 있었다. 이러한 결과로부터 제분에 의한 semolina의 이화학적 특성변화가 많이 일어남을 알 수 있으며, 부가적인 제면특성 검사를 통해 FS의 면류가공 적용이 가능하리라 생각된다.

• 한국대기환경학회지
• /
• 제21권6호
• /
• pp.639-647
• /
• 2005

A single particle analytical technique, named low-Z particle electron probe X-ray microanalysis (EPMA), was applied to characterize samples collected at a subway station and ambient samples in Seoul. According to their chemical composition, many distinctive particle types were identified. For samples collected at the subway station platform, the major chemical species are carbon-rich, organic, aluminosilicates (AlSi), AlSi/C, AlSi/$CaCO_{3},\;CaCO_{3},\;SiO_{2},\;and\;Fe_{2}O_{3}$. For outdoor samples, carbon-rich, organic, AlSi, $CaCO_{3},\;SiO_{2},\;NaNO_{3},\;(Na,Mg)NO_{3},\;Na(CO_{3},NO_{3},SO_{4}),\;and\;(NH_{4})_2SO_4$, are abundantly encountered. Samples collected at the subway station show very high contents of $Fe_{2}O_{3}$, both in coarse and fine fractions, which come from brake block, subway train wheel, electric contact materials, etc. It is demonstrated that the single-particle characterization using this low-Z particle EPMA technique provided detailed information on various types of chemical species in indoor and outdoor samples.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2005년도 춘계학술대회
• /
• pp.310-313
• /
• 2005

The conical fluidizing system of a binary mixture of Geldart C powders and Geldart A particles was defined as the conical powder-particle fluidized bed. We used a cold conical powder-particle fluidized bed model having a 0.104m-I.D. and 0.6m-high with an apex angle of $10^{\circ}$ for fluidization of a binary powder-particle mixture of 50 $vol\%$ fine carbon black powders (HI-900L, Korea Carbon Black Co.) and coarse alumina particles $(90{\mu}m)$ under different superficial gas velocities (0-0.1 m/s). The differential bed pressure drop increases with increasing gas velocity, and it goes from zero to a maximum value with increasing or decreasing gas velocity. In the conical fluidized beds of fine powders, demarcation velocities of the partial fluidization, full fluidization, partial defluidization was not observed.

• 한국대기환경학회지
• /
• 제16권5호
• /
• pp.445-451
• /
• 2000

To estimate dry deposition flux of 12 elements in aerosols, aerosol particles were sampled by a low-pressure impactor(LPI) and a dust jar. The concentrations of 12 elements in aerosol particle and dry deposition were analyzed by a PIXE analysis using as a 2.0 MeV-proton beam. The mean dry deposition velocities of 12 elements were estimated by ranges of 0.74∼2.62 cm/sec. The results showed that the highest value was 3.26 cm/sec for Ca and the lowest value 0.74 cm/sec for Fe. The dry deposition flux for elements was calculated as a function of particle size by 1-step method and 12-step method. In this work, dry deposition velocities were computed with the two existing models; the coarse-particle fraction(4∼30 mm diameter) using the dry deposition velocity model of the Noll and Fang(1998) and the fine-particle fraction (0.05∼4mm diameter) using the Shemel and Hodgson(1980) model. The ratios of the mean calculated/measured fluxes were 3.59 for 1-step method and 0.60 for 12-step method respectively.

• 동력기계공학회지
• /
• 제9권4호
• /
• pp.130-136
• /
• 2005

The effects of additional Mg content, the size and volume fraction of reinforcement phase on the mechanical properties of ceramic particle reinforced aluminium matrix composites fabricated by pressureless metal infiltration process were investigated. The hardness of $SiC_p/AC8A$ composites increased gradually with an increase in the additive Mg content, while the bending strength of $SiC_p/AC8A$ composites increased with an increase in additive Mg content up to 5%. However, this decreased when the level of additive Mg content was greater than 5% due to the formation of coarse precipitates by excessive Mg reaction and an increase in the porosity level. The hardness and strength of the composites increased with decreasing the size of SiC particle. It was found that the composites with smaller particles enhanced the interfacial bonding than those with bigger particles from fractography of the composites. The hardness of $Al_2O_{3p}/AC8A$ composites increased gradually with an increase in the volume fraction, however, the bending strength of $Al_2O_{3p}/AC8A$ composites decreased when the volume fraction of alumina particle was greater than 40% owing to the high porosity level.

• International Journal of Advanced Culture Technology
• /
• 제12권2호
• /
• pp.334-344
• /
• 2024

In Dangjin, Chungcheongnam-do, there are not only power plants and large steel complexes, but also small and medium-sized air pollutant emission facilities. The dust generated by these facilities has a very small particle size and a large surface area due to condensation and physical and chemical reactions, and is discharged containing various harmful substances. Therefore, this study analyzed the distribution of particulate matter and heavy metal concentrations by particle size in the vicinity of the steel complex, residential area, and reference point using an eight-stage Cascade Impactor. Overall, the direct impact sites with a short distance from the steel complex had the highest concentration, followed by the indirect impact sites, and the non-impact sites had the lowest concentration, indicating that they are directly affected by the steel complex. The atmospheric dust concentration distribution showed a bimodal distribution with a minimum value around the 1.1 to 2.1 ㎛ particle diameter. However, during the yellow dust event, the maximum concentration was biased toward coarse particles. The proportion of PM2.5 in the dust tended to be higher in winter, while the ratio between PM2.5 and PM10 was relatively higher in spring. Regardless of the location of the impact point, heavy metals in the dust were dominated by iron and aluminum, followed by zinc, lead, and manganese.