• Composites Research
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• v.34 no.2
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• pp.115-122
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• 2021

SMC(Sheet molding compound) composite is mainly used for forming of vehicle's body. Considering the car accident, it is essential to research the impact behavior and characteristics of materials. It is difficult to identify them because the impact process is completed in a short time. Therefore, the impact damage analysis using FE(finite element) model is required for the impact behavior. The impact damage analysis requires the parameters for the damage model of SMC composite. In this paper, ANN(artificial neural network) technique is applied to obtain the parameters for the damage model of SMC composite. The surrogate model by ANN was constructed with the result in LS-DYNA. By comparing the absorption energy in drop weight test with the result of ANN model, the optimized parameters were obtained. The acquired parameters were validated by comparing the results of the experiment, the FE model and the ANN model.

• Transactions of Materials Processing
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• v.31 no.1
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• pp.17-22
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• 2022

Hot stamping is widely used to manufacture structural parts to satisfy requirements of eco-friendly vehicles. Recently, hot forming technology using uncoated steel sheet is being studied to reduce cost and solve patent problems. In particular, research is focused on process technology capable of suppressing the generation of an oxide layer. To evaluate the oxide layer in the hot stamping process, Gleeble testing machine can be used to evaluate the oxide layer by controlling the temperature history and the atmosphere condition. At this time, since cooling by gas injection is impossible to protect the oxide layer on the surface of a specimen, research on a method for securing a quenching speed through natural cooling is required. This paper proposes a specimen shape design method to secure a target quenching speed through natural cooling when evaluating the oxide layer of an un-coated boron steel sheet by Gleeble test. For the evaluation of the oxide layer of the un-coated steel sheet through the Gleeble test, dog-bone and rectangular type specimens were used. In consideration of the hot stamping process, the temperature control conditions for the Gleeble test were set and the quenching speed according to the specimen shape design was measured. Finally, the quenching speed sensitivity according to shape parameter was analyzed through regression analysis. A quenching speed prediction equation was then constructed according to the shape of the specimen. The constructed quenching speed prediction equation can be used as a specimen design guideline to secure a target quenching speed when evaluating the oxide layer of an un-coated boron steel sheet by the Gleeble test.

• Proceedings of the Korean Society of Near Infrared Spectroscopy Conference
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• 2001.06a
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• pp.1530-1530
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• 2001

The objectives of this study were to develop models to predict quality parameters of Korean bee-honeys by visible and NIR spectroscopic technique. Two kinds of bee-honey fronl acacia and polyflower sources were tested in this study. The honeys were harvested in the spring of 2000 and stored in the storage facility at 20$^{\circ}C$ during experiments. Total of 394 samples of honey were analyzed. Reflectance spectra, moisture contents, ash, invert sugar, sucrose, F/G (fructose/glucose) ratio, HMF (hydroxymethyl furfural), and C12/C13 ratio of honeys were measured. The average values for the tested honeys were 19.9% of moisture contents, 0.12% of ash, 68.4% of invert sugar, 5.7% of sucrose, 1.27 of F/G(fructose/glucose) ratio, 14.4 mg/kg of HMF, and -19.1 of C12/C13 ratio. A spectrophotometer, equipped with a single-beam scanning monochromator (NIR Systems, Model 6500, USA) and a horizontal setup module, was used to collect reflectance data from honey. The reflectance spectra were measured in wavelength ranges of 400∼2,498 nm. with 2 nm of interval. Thirty-two repetitive scans were averaged, transformed to log(1/Reflectance), and then were stored in a microcomputer file, forming one spectrum per measurement. A sample cell and reflectance plate were made to hold honey samples constantly. Spectra of honey samples were divided into a calibration set and a validation set. The calibration set was used during model development, and the validation set was used to predict quality parameters from unknown spectra. The PLS(Partial Least Square) models were developed to predict the quality parameters of honeys. The first and the second derivatives of raw spectra were also used to develop the models with proper smoothing gap. The MSC (multiplicative scatter correction) and the SNV & Dtr.(standard normal variate and detranding) preprocessing were applied to all spectra to minimize sample-to-sample light scatter differences. The PLS models showed good relationships between predicted and measured quality parameters of honeys in the wavelength range of 1100∼2200 nm. However, the PLS analysis was not good enough to predict HMF of honeys.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1367-1372
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• 2014

As the awareness of the environmental crisis has recently increased around the world, numerous studies in the transport industry have been conducted to solve this problem through lightweight car bodies. The hot-stamping process has been presented as solution to achieve a light weight. Hot-stamping is a method that is used to obtain ultra-high strength steel (1,500 MPa or greater) by simultaneously forming and cooling boron steel in a press die after heating it to a temperature of $900^{\circ}C$ or above. This study involved a, fundamental examination of laser parameters to investigate the laser weldability of boron steel. As a result, the following optimum parameters for the shielding gas were found: Q = 20 l/min, ${\alpha}=40^{\circ}$, d = 20mm, and l = 0 mm. The hardness of butt weldment increasesed sharply as a result of martensite formation at the fusion zone.

• Journal of Drive and Control
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• v.12 no.4
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• pp.60-70
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• 2015

A front-end loader (FEL) mounted on an agricultural tractor is one of the most commonly used implements for farm work. However, when the tractor carries material using the bucket attached to the FEL on a sloping ground, the materials can spill or roll back over the operator due to the tilted body, thereby requiring the bucket surface to remain level at a constant value regardless of varying slopes. In this study, an active system for controlling the angle of the FEL bucket on a tractor based on the real-time measurement of ground slopes was developed to enable the bucket to constantly remain level. A FEL simulator operated based on an electro hydraulic proportional valve (EHPV) was constructed in the laboratory to develop a proportional-integral-derivative (PID) controller forming a virtual electronic control unit (ECU) on the computer, which could automatically adjust the bucket angles depending on varying input angles while sending SAE-J1939 associated messages via CAN BUS to the EHPV. The different parameter values for the PID controller due to the gravity effect of the bucket were determined using a manual PID tuning method while assuming that the tractor travels on either an ascending slope or a descending slope. The developed PID control-based self-leveling system showed a mean of steady-state errors of within $1^{\circ}$ and a mean of delayed times of ~ 0.8s when the step input of $+20^{\circ}$ was given, implying that the developed system and control algorithm would be effective in maintaining the bucket angle at a certain value. Future studies include the improvement of the control algorithm to reduce such a time delay as well as the application of the developed algorithm to the FEL mounted on a tractor tested at a testing ground.

• Korean Journal of Ecology and Environment
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• v.37 no.2 s.107
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• pp.205-212
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• 2004

Phosphorus cycle was studied in a deep stratified reservoir in summer monsoon area (Lake Soyang, Korea) by surveying phosphorus input from the watershed and the movement of phosphorus within the reservoir. And the spatial and temporal distribution of phosphorus was modeled with a 2-dimensional water quality model (CE-QUAL-W2), Phosphorus loading was calculated by measuring TP in the main inflowing river (the Soyang River) accounting for 90% of watershed discharge. TP of the Soyang River showed a large daily variation with the flow rate. High phosphorus loading occurred during a few episodic storm runoff laden with suspended sediments and phosphorus. Because storm runoff water on rainy days have lower temperature, it plunges into a depth of same temperature (usually below 20m depth), forming an intermediate turbidity layer with a thickness of 20 ${\sim}$ 30 m. Because of stable thermal stratification in summer the intermediate layer water of high phosphorus content was discharged from the dam through a mid-depth outlet without diffusing into epilimnion. The movement of runoff water within the reservoir, and the subsequent distribution of phosphorus were well simulated by the water quality model showing a good accuracy. The major parameter for the calibration of phosphorus cycle was a settling velocity of detritus, which was calibrated to be 0.75 m ${\cdot}$ $day^{-1}$. It is concluded that the model can be a good simulator of limnological phenomena in reservoirs of summer monsoon area.

• Journal of the Korean Applied Science and Technology
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• v.37 no.3
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• pp.484-495
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• 2020

This study is a mixed surfactant (MimicLipid-MSM1000) that forms the same structure as that of the stratum corneum, sucrose distearate, polyglyceryl-2 dioleate, fermented squalane, ergosterol, 10-hydroxystearic acid, mixture consisting of was synthesized. When using 2~5 wt% of this mixed surfactant, it was possible to make an artificial skin mimetic that forms a multi-layer lamellar structure of 5~30 layers. An emulsion was prepared using this mixed surfactant, and a multi-layered lamellar phase was formed and analyzed mechanically. The appearance of this surfactant was a light brown hard wax, the hydrophilic lipophilic balance (HLB) was 12.53, the critical parameter value was 0.987, and the acid value was 0.13. Stability according to pH change was also stable in acidic (3.8), neutral (7.2) and alkaline (10.8). The particle size of the liquid crystal was found to be the most stable maltese cross lamellar crystalline droplet at 5~25mm. The size of the emulsified particles according to the change in the speed of the homo agitator is 2500 rpm (17.9mm±2.6mm), 3500rpm (12.5mm±2.1mm), 4500rpm (6.2mm±1.8mm) particles were formed. Liquid crystal forming particles were observed through a polarization microscope, and the formation structure of the liquid crystal was precisely analyzed with a scanning electron microscope (cryo-SEM). As an application field, it is expected that it will be widely applicable to the development of various prescriptions, such as various skin care cosmetics, makeup care cosmetics, and scalp protection cosmetics, by using a skin-mimicking surfactant.

• Korean Journal of Mineralogy and Petrology
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• v.34 no.1
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• pp.41-56
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• 2021

The characteristics of the six rock cleavages(R1~H2) in Jurassic Hapcheon granite were analyzed using the distribution of ① microcrack lengths(N=230), ② microcrack spacings(N=150) and ③ Brazilian tensile strengths(N=30). The 18 cumulative graphs for these three factors measured in the directions parallel to the six rock cleavages were mutually contrasted. The main results of the analysis are summarized as follows. First, the frequency ratio(%) of Brazilian tensile strength values(kg/㎠) divided into nine class intervals increases in the order of 60~70(3.3) < 140~150(6.7) < 100~110·110~120(10.0) < 90~100(13.3) < 80~90(16.7) < 120~130·130~140(20.0). The distribution curve of strength according to the frequency of each class interval shows a bimodal distribution. Second, the graphs for the length, spacing and tensile strength were arranged in the order of H2 < H1 < G2 < G1 < R2 < R1. Exponent difference(λS-λL, Δλ) between the two graphs for the spacing and length increases in the order of H2(-1.59) < H1(-0.02) < G2(0.25) < G1(0.63) < R2(1.59) < R1(1.96)(2 < 1). From the related chart, the six graphs for the tensile strength move gradually to the left direction with the increase of the above exponent difference. The negative slope(a) of the graphs for the tensile strength, suggesting a degree of uniformity of the texture, increases in the order of H((H1+H2)/2, 0.116) < G((G1+G2)/2, 0.125) < R((R1+R2)/2, 0.191). Third, the order of arrangement between the two graphs for the two directions that make up each rock cleavage(R1·R2(R), G1·G2(G), H1·H2(H)) were compared. The order of arrangement of the two graphs for the length and spacing is reverse order with each other. The two graphs for the spacing and tensile strength is mutually consistent in the order of arrangement. The exponent differences(ΔλL and ΔλS) for the length and spacing increase in the order of rift(R, -0.08) < grain(G, 0.14) < hardway(H, 0.75) and hardway(H, 0.16) < grain(G, 0.23) < rift(R, 0.45), respectively. Fourth, the general chart for the six graphs showing the distribution characteristics of the microcrack lengths, microcrack spacings and Brazilian tensile strengths were made. According to the range of length, the six graphs show orders of G2 < H2 < H1 < R2 < G1 < R1(< 7 mm) and G2 < H1 < H2 < R2 < G1 < R1(≦2.38 mm). The six graphs for the spacing intersect each other by forming a bottleneck near the point corresponding to the cumulative frequency of 12 and the spacing of 0.53 mm. Fifth, the six values of each parameter representing the six rock cleavages were arranged in the order of increasing and decreasing. Among the 8 parameters related to the length, the total length(Lt) and the graph(≦2.38 mm) are mutually congruent in order of arrangement. Among the 7 parameters related to the spacing, the frequency of spacing(N), the mean spacing(Sm) and the graph (≦5 mm) are mutually consistent in order of arrangement. In terms of order of arrangement, the values of the above three parameters for the spacing are consistent with the maximum tensile strengths belonging to group E. As shown in Table 8, the order of arrangement of these parameter values is useful for prior recognition of the six rock cleavages and the three quarrying planes.

• Economic and Environmental Geology
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• v.24 no.2
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• pp.131-150
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• 1991

The Weolseong diatreme was temporally and spatially related to the intrusion of the Gadaeri granite, and was -mineralized by meteoric aqueous fluids. In the Nokdong As-Zn deposit, pyrite, aresenopyrite and sphalerite are the most abundant sulfide minerals. They are associated with minor amount of magnetite, pyrrhotite, chalcopyrite and cassiterite, and trace amounts of Pb-Sb-Bi-Ag sulphosalts. The AsZn ore probably occurred at about $350^{\circ}C$ according to fluid inclusion and compositional data estimated from the arsenic content of arsenopyrite and iron content of sphalerite intergrown with pyrrhotite + chalcopyrite + cubanite. Heating studies of fluid inclusions in quartz indicate a temperature range between 180 and $360^{\circ}C$, and freezing data indicate a salinity range from 0.8 to 4.1 eq.wt % NaCl. The coexisting assemblage pyrite + pyrrhotite + arsenopyrite suggests that $H_2S$ was the dominate reduced sulfur species, and defines fluid parameter thus: $10^{-34.5}$ < ${\alpha}_{S_2}$ < $10^{-33}$, $10^{-11}$ < $f_{S_2}$ < $10^{-8}$, -2.4 < ${\alpha}_{S_2}$ < -1.6 atm and pH= 5.2 (sericte stable) at $300^{\circ}C$. The sulfur isotope values ranged from 1.8 to 5.5% and indicate that the sulfur in the sulfides is of magmatic in origin. The carbon isotope values range from -7.8 to -11.6%, and the oxygen isotope values from the carbonates in mineralized wall rock range from 2 to 11.4%. The oxygen isotope compositions of water coexisting with calcite require an input of meteoric water. The geochemical data indicate that the ore-forming fluid probably was generated by a variety of mechanisms, including deep circulation of meteoric water driven by magmatic heat, with possible input of magniatic water and ore component.

• The Journal of Small Business Innovation
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• v.19 no.4
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• pp.19-39
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• 2016

With increasing adoption of smart products and complexity, companies have shifted their strategies from stand alone and competitive strategies to business ecosystem oriented and cooperative strategies. The win-win growth of business refers to corporate efforts undertaken by companies to pursue the healthiness of business between conglomerates and partnering companies such as suppliers for mutual prosperity and a long-term corporate soundness based on their business ecosystem and cooperative strategies. This study is designed to validate a theoretical proposition that the win-win growth strategy of Samsung Electronics and cooperative efforts among companies can create a healthy business ecosystem, based on results of case studies and surveys. In this study, a level of global market access of small and mid-sized companies is adopted as the key achievement index. The foreign market entry is considered as one of vulnerabilities in the ecosystem of small and mid-sized enterprises (SMEs). For SMEs, the global market access based on the research and development (R&D) has become the critical component in the process of transforming them into global small giants. The results of case studies and surveys are analyzed mainly based on a model of a virtuous cycle of Creativity, Opportunity, Productivity, and Proactivity (the COPP model) that features the characteristics of the healthiness of a business ecosystem. In the COPP model, a virtuous circle of profits made by the first three factors and Proactivity, which is the manifestation of entrepreneurship that proactively invests and reacts to the changing business environment of the future, enhances the healthiness of a given business ecosystem. With the application of the COPP model, this study finds major achievements of the win-win growth of Samsung Electronics as follows. First, Opportunity plays a role as a parameter in the relations of Creativity, Productivity, and creating profits. Namely, as companies export more (with more Opportunity), they are more likely to link their R&D efforts to Productivity and profitability. However, companies that do not export tend to fail to link their R&D investment to profitability. Second, this study finds that companies with huge investment on R&D for the future, which is the result of Proactivity, tend to hold a large number of patents (Creativity). And companies with significant numbers of patents tend to be large exporters as well (Opportunity), and companies with a large amount of exports tend to record high profitability (Productivity and profitability), and thus forms the virtuous cycle of the COPP model. In addition, to access global markets for sustainable growth, SMEs need to build and strengthen their competitiveness. This study concludes that companies with a high level of proactivity to invest for the future can create a virtuous circle of Creativity, Opportunity, Productivity, and Proactivity, thereby providing a strategic implication that SMEs should invest time and resources in forming such a virtuous cycle which is a sure way for the SMEs to grow into global small giants.