• 화약ㆍ발파
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• 제32권3호
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• pp.1-9
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• 2014

벤치발파에서 발파에 의한 암석의 파쇄입도는 적재, 운반과 파쇄로 이어지는 후속공정에 직접적으로 영향을 미치고 있다. 본 연구에서는 전자뇌관을 사용하여 정확한 지연시차를 구현하였으며, 각 발파공에 대해 저항선 m당 1, 2, 3, 4, 5, 7, 10ms의 지연시차를 적용하여 실규모 시험을 통해 암석 파쇄입도를 측정하였다. 그 결과, 석회석 광산에서 저항선을 기준으로 약 6ms/m의 지연시차가 최소의 파쇄입도를 가지는 것으로 측정되었다. 또한, 파쇄입도 분포 분석을 통해 지연시차가 암석의 파쇄입도에 변화를 줄 수 있는 요소로 정의될 수 있으며, 지연시차를 통해 파쇄입도를 조절 가능하다고 사료된다.

• Geomechanics and Engineering
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• 제15권5호
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• pp.1047-1059
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• 2018

This paper focuses on the cracking and fragmentation process in rock materials containing a pair of non-parallel flaws, which are through the specimen thickness, under vertical compression. Several numerical experiments are conducted with varying flaw arrangements that affect the initiation and tensile wing cracks, shear crack growth, and crack coalescing behaviors. To obtain realistic numerical results, a parallelized peridynamics formulation coupled with a finite element method, which is able to capture arbitrarily occurring cracks, is employed. From previous studies, crack initiation and propagation of tensile wing cracks, horsetail cracks, and anti-wing cracks are well understood along with the coalescence between two parallel flaws. In this study, the coalescence behaviors, their fragmentation sequences, and the role of an x-shaped shear band in rock material containing two non-parallel flaws are discussed in detail on the basis of simulation results strongly correlated with previous experimental results. Firstly, crack initiation and propagation of tensile wing cracks and shear cracks between non-parallel flaws are investigated in time-history and then sequential coalescing behavior is analyzed. Secondly, under the effect of varying inclination angles of two non-parallel flaws and overlapping ratios between a pair of non-parallel flaws, the cracking patterns including crack coalescence, fragmentation, and x-shaped shear band are investigated. These numerical results, which are in good agreement with reported physical test results, are expected to provide insightful information of the fracture mechanism of rock with non-parallel flaws.

• 환경영향평가
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• 제11권3호
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• pp.117-127
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• 2002

This study tested the usefulness of landscape indices for quantifying forest fragmentation due to linear development projects. Research was carried out in the middle-upper Nakdong River watershed, which has been affected by the expressway building, or national road-widening. Landscape indices were calculated from the forest cover maps before and after road-building using FRAGSTATS 3.1. We could successfully demonstrate the forest fragmentation based on landscape indices; (1) patch size decreased, and edge density and patch density increased (2) roads simplified patch shapes, especially in the larger patches, (3) patch core area size decreased, and core area density increased, (4) the distance increased between the focal patch and each of the other patches within the search radius (=1km) as a result of roads. We suggest several important needs for future researches, including continued investigation of scaling issues, development of indices that measure specific components of spatial pattern, and study of the relationships between forest fragmentation and ecological processes.

• Reproductive and Developmental Biology
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• 제35권4호
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• pp.499-502
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• 2011

Aurora A kinase is a mitotic serine/threonine kinase whose proposed functions include the maturation of centrosomes, G2/M transition, alignment of chromosomes at metaphase, and cytokinesis. In this study, we investigated the effect of MLN8237, an aurora A kinase inhibitor, on the postovulatory aging of oocytes based on the frequency of oocyte fragmentation, cdk1 kinase activity, and cyclin B degradation. The fragmentation of ovulated oocytes during prolonged culture was inhibited by treatment with MLN8237 in a concentration-dependent manner. The frequency of fragmented oocytes was significantly lower in oocytes treated with 2 ${\mu}M$ MLN8237 (13%) than in control oocytes (64%) after two days of culture. Most of the control (non-fragmented) oocytes (91%) were activated after two days of culture. In comparison, only 22% of the MLN8237-treated oocytes were activated; the rest of the oocytes (78%) were still in metaphase with an abnormal spindle and dispersed chromosomes. Next, cdk1 activity and the level of cyclin B were examined. The level of cyclin B and cdk1 activity in MLN8237-treated oocytes were nearly equal to those in control oocytes. Our results indicate that MLN8237 inhibited the fragmentation of ovulated oocytes during prolonged culture, although it blocked the spontaneous decrease in activity of cdk1 and degradation of cyclin B. This mechanism of inhibition is different from that in oocytes treated with nocodazole, which have high levels of cdk1 activity and cyclin B.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3583-3587
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• 2010

Furoxanthiols PFT and BPFT possessing thiomethyl or thiobenzyl groups in the furoxan ring were designed and synthesized as potential light-sensitive alkyne precursors on a gold surface. The synthesis of thiofuroxans PFT and BPFT was performed from the corresponding halofuroxans 1b and 2c, respectively, by the substitution with potassium thioacetate in ethyl acetate/ethanol or DMF, followed by basic hydrolysis as the key reactions. Electron-beammediated fragmentation of furoxans 1c and 2d in a mass spectrometer afforded the corresponding aryl alkyne fragments, with the evolution of NO in high preference. In the cases of thiofuroxans PFT and BPFT, carbon-sulfur bond cleavage was observed as a representative fragmentation, producing M-SH and M-SAc peaks, which competed with the release of NO. In the fragmentation of mono-aryl furoxan 1c, the release of molecule of NO was predominately observed to produce an M-NO fragment as a base peak by the formation of trimembered thiiranium or azirine intermediate.

• 터널과지하공간
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• 제21권1호
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• pp.82-92
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• 2011

입체사진측량기법이란 대상면에 대하여 두 장 이상의 사진 영상을 취득한 후 이 영상을 이용하여 대상면의 공간 정보를 추출하는 방법이다. 본 연구에서는 발파 현장에서 발생되는 파쇄암들의 파쇄도 분석에 입체사진 측량기법을 적용하였다. 실내실험을 통하여 평면적으로 배치된 암석들의 파쇄도 분석에 2차원 영상처리기법과 입체사진측량기법을 적용 및 그 결과를 비교하였고, 입체사진측량기법과 통계 분석을 통하여 실내실험 및 현장 실험에서 파쇄암 더미의 입도분포 추정 가능성을 평가하였다.

• Mass Spectrometry Letters
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• 제9권4호
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• pp.91-94
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• 2018

Bilin tetrapyrroles are metabolic products of the breakdown of porphyrins within a species. In the case of mammals, these bilins are formed by the catabolism of heme and can be utilized as either biomarkers in disease or as an indicator of human waste contamination. Although a small subset of bilin tandem mass spectrometry reports exist, limited data is available in online databases for their fragmentation. The use of fragmentation data is important for metabolomics analyses to determine the identity of compounds detected within a sample. Therefore, in this study, the fragmentation of bilins generated by positive ion mode electrospray ionization is examined by collision-induced dissociation (CID) as a function of collision energy on an FT-ICR MS. The use of the FT-ICR MS allows for high mass accuracy measurements, and thus the formulas of resultant product ions can be ascertained. Based on our observations, fragmentation behavior for hemin, biliverdin and its dimethyl ester, phycocyanobilin, bilirubin, bilirubin conjugate, mesobilirubin, urobilin, and stercobilin are discussed in the context of the molecular structure and collision energy. This report provides insight into the identification of structures within this class of molecules for untargeted analyses.

• 화약ㆍ발파
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• 제36권4호
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• pp.9-15
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• 2018

발파에 의한 암석의 파쇄도는 적재, 운반과 2차 파쇄로 이어지는 후속공정에 직접적인 영향을 미치므로 파쇄도의 조절은 발파 효율성과 생산비용을 평가하는데 필수적이다. 본 연구에서는 인공절리의 방향에 따른 암석의 파쇄도에 대해 분석하였다. 갱내 암반에 수직 및 수평인공절리를 생성한 후 발파실험을 수행하였다. 생성된 암석파쇄물의 입도분포는 2차원 영상해석 프로그램인 split-desktop으로 평가하였다. 평가결과 수평인공절리가 수직인공절리에 비해 전체적인 암석파쇄물의 크기가 작게 평가되었고, 다양한 크기로 암석파쇄물이 분포하였다. 인공절리의 방향에 따라 대괴발생을 억제하고 암석파쇄물을 일정한 크기 이하로 조절 할 수 있을 것으로 판단된다.

• 생태와환경
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• 제54권1호
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• pp.61-70
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• 2021

The effects of forest type and fragmentation of forests by a road on the beetle community were investigated in the Gwangneung Forest, South Korea. Beetles were collected monthly using pitfall traps and by sweeping at 16 sites (eight in coniferous forests and eight in deciduous forests) for one year from April 1993 to April 1994, excluding winter. A total of 17,616 beetles belonging to 271 species from 39 families were collected. Among them, Synuchus cycloderus was the dominant species, with 14,060 individuals accounting for 80% of the total population. The influence of forest type (coniferous and deciduous) or sampling region (fragmented by a road) on species richness(number of species) was observed. We found that species richness was substantially different depending on the sampling method and taxa used. Beetles collected using pitfall traps responded more sensitively to habitat types than those collected by sweeping. Four dominant families differently responded to forest fragmentation and forest types. Carabidae was influenced by forest fragmentation, whereas Staphylinidae and Curculionidae were influenced by forest types. Chrysomelidae was not influenced.

• Geomechanics and Engineering
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• 제34권5호
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• pp.547-559
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• 2023

We evaluated the applicability of machine learning techniques and the Kuz-Ram model for predicting the mean fragmentation size in open-pit mines. The characteristics of the in-situ rock considered here were uniaxial compressive strength, tensile strength, rock factor, and mean in-situ block size. Seventy field datasets that included these characteristics were collected to predict the mean fragmentation size. Deep neural network, support vector machine, and extreme gradient boosting (XGBoost) models were trained using the data. The performance was evaluated using the root mean squared error (RMSE) and the coefficient of determination (r²). The XGBoost model had the smallest RMSE and the highest r² value compared with the other models. Additionally, when analyzing the error rate between the measured and predicted values, XGBoost had the lowest error rate. When the Kuz-Ram model was applied, low accuracy was observed owing to the differences in the characteristics of data used for model development. Consequently, the proposed XGBoost model predicted the mean fragmentation size more accurately than other models. If its performance is improved by securing sufficient data in the future, it will be useful for improving the blasting efficiency at the target site.