• Journal of the Mineralogical Society of Korea
• /
• v.32 no.3
• /
• pp.185-200
• /
• 2019

This study aimed to liberate gold from invisible gold concentrate (Au = 1,840.00 g/t) through microwave nitric acid leaching experiments. For the purpose, this study conducted microwave-nitric acid leaching experiments and examined nitric acid concentration effect, microwave leaching time effect and sample addition effect. The results of the experiments were as follows: Au (gold) contents were not detected in all of the microwave leaching conditions. In the insoluble-residue, weight loss rate tended to decrease as the nitric acid concentration, microwave leaching time and sample addition increased. In an XRD analysis with solid-residue, it was suggested that gypsum and anglesite were formed due to dissolution of calcite and galena by nitric acid solution. When a fire assay was carried out with insoluble-residue, it was discovered that gold contents of the solid-residue were 1.3 (Au = 2,464.70 g/t) and 28.8 (52,952.80 g/t) times more than those of concentrate. But in the gold contents recovered, a severe gold nugget effect appeared. It is expected that the gold nugget effect will decrease if a sampling method of concentrate is improved in the microwave-nitric acid leaching experiments and filtering paper with smaller pore size is used for leaching solution and burned filter paper is used for sampling in lead-fire assay.

• Journal of the korean academy of Pediatric Dentistry
• /
• v.27 no.1
• /
• pp.113-121
• /
• 2000

This study was aimed to provide an epidemiologic study so that we could accommadate their orthodontic needs adequately and to obtain the reliable quantitative information regarding the characteristics of orthodontic patients who visited the Department of pediatric dentistry, Chonnam National University Hospital from 1986 to 1999, October. The results were as follows. 1 The total number of orthodontic patients were 1,381(male 658, female 723) and the number of annual patients showed irregular trend and the number of male were slightly higher than that of female. 2. According to the investigation made by age group, the group of under 5 years, 6 to 7, 8 to 9, 10 to 11, 12 to 13 and above 14 years showed 8.4%, 29.6%, 34.3%, 21.2%, 5.7% and 0.8%, respectively. 3. The patients corresponding to primary dentition were 15.7% of total patients and mesial step, distal step and flush terminal plane were 83%, 4.6% and 12.4% respectively. By the way 82% of mesial step had anterior crossbite at the same time. 4. The patients corresponding to Angle classification were 84.3% of total patients and Class I malocclusion, Class II div. 1, Class II div. 2 and Class III was 34.7%, 34.6%, 2.1% and 28.6%, respectively.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.1
• /
• pp.69-79
• /
• 2008

Prediction of ground condition ahead of tunnel face might be the most important factor to prevent collapse during tunnel excavation. In this study, a non-destructive method to evaluate the phase velocity in model rock mass using wavelet transform of surface wave was proposed aiming at ground condition assessment ahead of tunnel face. Model tests using gypsum as a rocklike material composed of two layers were performed. A Piezoelectric actuator with frequencies ranging from 150 Hz to 5 kHz was selected as a harmonic source. The acceleration history was measured with two accelerometers. Wavelet transform analysis was used to obtain the dispersion curves from the measured data. The experimental results showed that the near-field effects can be neglected if the distance between two receivers is chosen to be three times the wavelength. A simple inversion method using weighted factor based on the normal distribution was proposed. The inversion results showed that the predicted phase velocity agreed reasonably well with the measured one when the wavelength influence factor was 0.2. The depth of propagation of surface wave was from 0.42 to 0.63 times the wavelength. The range of wavelength varying with phase velocity in dispersion curve matched well with that estimated by inversion technique.

• Journal of Apiculture
• /
• v.32 no.1
• /
• pp.27-39
• /
• 2017

PCR-chip-based ultra-rapid multiplex PCRs for detection of six major infectious pathogens in honeybee were developed. The 6 kinds of major infectious pathogens in honeybee included Paenibacillus larvae causing American Foulbrood, Melissococcus plutonius causing European Foulbrood as bacteria, Ascosphaera apis (Chalkbrood), Aspergillus flavus (Stonebrood), Nosema apis and Nosema ceranae (Nosemosis) as fungi. The developed PCR-chip-based ultra-rapid multiplex PCR showed successful amplification for all six major pathogens in the presence of more than $10^3$ molecules. The time for confirming amplification (Threshold cycles; Ct-time) was about 7 minutes for two species, and about 9 minutes for four species. Total 40 cycles of PCR took 11 minutes 42 seconds and time for melting point analysis was 1 minute 15 seconds. Total time for whole PCR detection was estimated 12 minutes 57 seconds (40 cycles of PCR and melting point analysis). PCR-chip based ultra-rapid multiplex PCR using standard DNA substrates showed close to 100% accuracy and no false-amplification was found with honeybee genomic DNA. Ultra-rapid multiplex PCR is expected to be a fast and efficient pathogen detection method not only in the laboratory but also in the apiary field.

• The Journal of Engineering Geology
• /
• v.33 no.4
• /
• pp.573-586
• /
• 2023

Joints or weak planes can induce anisotropy in the strength and deformability of fractured rock masses. Comprehending this anisotropic behavior is crucial to engineering geology. This study used plaster as a friction material to mold specimens with a single joint. The strength and deformability of the specimens were measured in true triaxial compression tests. The measured results were compared with three-dimensional numerical analysis based on the distinct element method, conducted under identical conditions, to assess the reliability of the modeled values. The numerical results highlight that the principal stress conditions in the field, in conjunction with joint orientations, are crucial factors to the study of the strength and deformability of fractured rock masses. The strength of a transversely isotropic rock mass derived numerically considering changes in the dip angle of the joint notably increases as the intermediate principal stress increases. This increment varies depending on the dip of the joint. Moreover, the interplay between the dip direction of the joint and the two horizontal principal stress directions dictates the strength of the transversely isotropic rock mass. For a rock mass with two joint sets, the set with the steeper dip angle governs the overall strength. If a rock bridge effect occurs owing to the limited continuity of one of the joint sets, the orientation of the set with longer continuity dominates the strength of the entire rock mass. Although conventional three-dimensional failure criteria for fractured rock masses have limited applicability in the field, supplementing them with numerical analysis proves highly beneficial.

• Geotechnical Engineering
• /
• v.11 no.3
• /
• pp.139-162
• /
• 1995

The possibility of the development of gas driven hydrofractures at the Waste Isolation Pilot Plant(WIPP) is investigated through analytical and numerical calculations and through laboratory experiments. First, an investigation of the chemical reactions involved shows that a large volume of gas could potentially be generated through the oxidation of iron in the waste. Simple ground water'flow calculations then show that unless regions of high permeability has been created, this gas volume will build up the pressure high enough to cause tensile damage in the horizontal planes of weakness or in the halite itself. The analytical calculations were performed using the concepts of linear elastic fracture mechanics and the numerical calculations were done using the finite element method. Also, laboratory tests were conducted to illustrate possible failure mechanisms. It is possible that after growing horizontal crack in the weaker anhydride layer, the crack could break out of this layer and propagate upward into the halite and toward the ground surface at an inclined argle of around 53$^{\circ}$ above horizontal. To prevent this latter phenomenon the anhydrite must have a fracture toughness less than 0.5590 times than that of the halite. Through the tests, three types of crack(radial vertical cracks, horizontal circular cracks and cone -shaped cracks) were observed.

• Analytical Science and Technology
• /
• v.14 no.4
• /
• pp.364-370
• /
• 2001

The corrosion behaviors of reinforcing steels were investigated under chloride ion contained in cement mortar including gypsum by the implementation of half cell potential measurement, EPMA analysis, exterior features, weight loss and extraction experiment. The acceleration test equipment accelerated corrosion of mild steel bar in a short period of time. From observing the exterior features and weight loss, we could evaluate the measure of corrosion. Also, from the extraction experiment of ${SO_4}^{2-}$ with $Cl^-$ ions contained in the ceramic mortar, we concluded that ${SO_4}^{2-}$ ion affected more on the corrosion mechanism in comparison to pH.

• Journal of the Korean Geotechnical Society
• /
• v.18 no.4
• /
• pp.33-43
• /
• 2002

Recently, as large constructions on the coast increase, an application of a surface layer stabilization method which is one of the improvement methods for dredged soft clay has increased. However, there are few studies about this. The purpose of this study is clarifying characteristics of ultra-soft marine clay and hardening agent. Also, it is verifying an optimal mixture ratio of hardening agent through the laboratory tests according to designed experiments and proving by statistical analysis and pilot tests. Laboratory tests were performed with proper hardening agent and test soil in accordance with the design of experiments. Regression equations between hardening agents materials and unconfined compressive strength were derived from the tests. The applicability of regression equations were also verified by pilot tests. From the test results, it was found that hardening agent materials(cement, slag, fly-ash, inorganic salts, arwin, gypsum etc.) have some effect upon compressive strength. The optimal mixture ratio which satisfies the required compressive strength was derived from the statistical analysis. The effect of ground improvement by cements and hardening agents was confirmed through the pilot tests. This study will suggest data for design or construction criteria of stabilization of surface layer on ultra-soft marine clay.

• Journal of the Korean Wood Science and Technology
• /
• v.45 no.3
• /
• pp.327-334
• /
• 2017

This study was carried out to investigate the formaldehyde emission of building materials and effect of carbonized-board (c-board) on formaldehyde reduction using a chamber method. As a result, reduction performance of formaldehyde was in the order of c-board (90%), c-bamboo board (84%), diatomite-based panel (82%), allophane-based tile (78%), Pinus densiflora timber (58%), MDF (54%) and gypsum-based board (46%) for approximately 12 days. In $1.9m^3$ chamber filled with particleboard (PB), the formaldehyde reduction performance of c-board was significantly increased with increasing input amount of c-board for 68 days. In particular, the formaldehyde emissions can be reduced above 40% and 75% by input rate of 10% and 30% c-board, respectively, in given ratio of chamber volume and PB area.

• Journal of the Mineralogical Society of Korea
• /
• v.28 no.2
• /
• pp.165-171
• /
• 2015

Dust samples collected from air in metropolitan areas of Busan and Ulsan were analyzed by phase contrast microscopy, phase contrast dispersion microscopy and SEM. Asbestos concentration in dust samples was lower than detection limit. Many fibrous materials were observed in dust samples, but most of them were organic fibers. Inorganic fibers such as rock fiber, ceramic fiber and gypsum were contained in the samples and non-fibrous minerals such as quartz, calcite and feldspar were also occasionally observed. Domestic law requires that asbestos in air dust is mainly analyzed by phase contrast microscopy. From this study, however, precise analysis of asbestos was almost impossible by this method only. As indicated in JIS method of Japan, therefore, count and identification of asbestos were more efficient by dispersion staining method after removing organic materials in samples by low temperature incinerator.