• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2023.05a
• /
• pp.115-116
• /
• 2023

This study aims to investigate and improve the carbon dioxide sequestration capability and the mechanical properties of non-hydraulic low calcium silicate cement especially designed for CO₂ reaction and ordinary Portland cement subjected to the carbonation curing facilitating pH swing method. Nitric acid (HNO₃) was utilized as an liquid for the mixing of cement paste to enhance the initial dissolution of Ca ions from the cements by promoting low pH environment and prevent the direct precipitation of Ca with the anion, owing to the high solubility of Ca(NO₃)₂ in water. The results presented that the higher the concentration of HNO₃, the higher the compressive strength and CO₂ sequestration (until 0.1 M). Ca dissolution caused by the harsh acid attack onto the anhydrous cement particle lead to the higher carbonation reaction degree, forming abundant CaCO₃ crystals after the reaction. However, cement paste mixed with excessively high concentration of HNO₃ presented deterioration due to the too harsh pH environment and abundant NO₃- ions which are known to retard the reaction of cement.

• Journal of Biomedical Engineering Research
• /
• v.28 no.2
• /
• pp.187-194
• /
• 2007

The purpose of this study is to determine the characteristics of ground reaction force(GRF) in golf swing for various slopes of flat lie and uphill lies of 5 and 10 degrees. Five right-handed professional golfers were selected for the experiment and the 7 iron club was used. We used four forceplates to measure GRF and synchronized with the three-dimensional motion analysis system. Results showed that slope did not affect the total time for golf swing, but the time until the impact had a tendency to slightly increase for the uphill lie(p<0.05). The medial-lateral GRF of the right foot increased toward the medial direction during back swing, but less increases were found with the angle of uphill lie(p<0.05). The GRF of the left foot increased rapidly toward the medial direction at the uncocking and the impact during down swing, but decreased with the increase in the angle of uphill lie(p<0.05). The anterior-posterior GRF of both feet showed almost the same for different slopes. With the slopes, the vertical GRF of the right foot increased, but the vertical GRF of left foot decreased(p<0.05). Uphill lies would have negative effect to provide the angular momentum during back swing, restricting pelvic and trunk rotations, and to provide the precise timing and strong power during down swing, limiting movements of body's center of mass. The present study could provide valuable information to quantitatively analyze the dynamics of golf swing. Further study would be required to understand detailed mechanism in golf swing under different conditions.

• Journal of the Mineralogical Society of Korea
• /
• v.30 no.4
• /
• pp.205-217
• /
• 2017

Mineral carbonation by indirect method has been studied by serpentinite as cation source. Through the carbonation of $CO_2$ and alkaline earth ions (calcium and magnesium) from serpentinite, the pure carbonates including $MgCO_3$ and $CaCO_3$ were synthesized. The extraction solvent used to extract magnesium (Mg) was ammonium sulfate ($(NH_4)_2SO_4$), and the investigated experimental factors were the concentration of $(NH_4)_2SO_4$, reaction temperature, and ratio of serpentinite to the extraction solvent. From this study, the Mg extraction efficiency of approximately 80 wt% was obtained under the conditions of 2 M $(NH_4)_2SO_4$, $300^{\circ}C$, and a ratio of 5 g of serpentinite/75 mL of extraction solvent. The Mg extraction efficiency was proportional to the concentration and reaction temperature. $NH_3$ produced from the Mg extraction of serpentinite was used as a pH swing agent for carbonation to increase the pH value. About 1.78 M of $NH_3$ as the form of $NH_4{^+}$ was recovered after Mg extraction from serpentinite. And, the main step in Mg extraction process of serpentinite was estimated by geochemical modeling.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2006.10a
• /
• pp.549-550
• /
• 2006

• KSBB Journal
• /
• v.16 no.5
• /
• pp.523-525
• /
• 2001

Curdlan is one biopolymer composed of ${\beta}$1,3-glucan and dissolved in a alkali solution but formed salt under neutral or acid condition. It was produced by Agrobactrium species and the separation process is necessary to make pure curdlan from the culture broth. The pH swing separation method was as feasible separation process using solubility changes with the pH difference. however, this method requires a lot of acid and alkali solution also produces a lot of waste. Therefore, an efficient process which could save energy and minimize toxic waste was developed. A density gradient separation process was developed in this research. High density sucrose solution was used as a separation agent. Curdlan was separated from the culture broth when the density of the sucrose solution was 1.15 g/L. Since the curdlan was produced on the surface of cell wall. the pre-treatment of culture broth was necessary. Curdlan recovery yield was increased up to 83% with the homogenization of the culture broth and further increased up to 87% with the treatment of alkai-acid solution.

• Economic and Environmental Geology
• /
• v.49 no.1
• /
• pp.13-22
• /
• 2016

The objectives of this study were to recover silica and iron oxides and $CO_2$ sequestration using serpentine via various acid dissolution and pH swing processes. Serpentine collected from Guhang-myeon in S. Korea were mainly composed of antigorite and magnetite consisting of $SiO_2$ (45.3 wt.%), MgO (41.3 wt.%), $Fe_2O_3$ (12.2 wt.%). Serpentine pulverized ($${\leq_-}75{\mu}m$$) and then dissolved in 3 different acids, HCl, $H_2SO_4$, $HNO_3$. Residues treated with acidic solution were recovered from the solution (step 1). And then the residual solution containing dissolved serpentine was titrated using $NH_4OH$. And pH of the solution increased up to pH=8.6 to obtain reddish precipitates (step 2). After recovery of the precipitates, the residual solution reacted with $CO_2$ and then pH increased up to pH=9.5 to precipitate white materials (step 3). The mineralogical characteristics of the original sample and harvested precipitates were examined by XRD, and TEM-EDS analyses. ICP-AES analysis was also used to investigate solution chemistry. The dissolved ions were Mg, Si, and Fe. The antigorite became noncrystralline silica after acid treatment (step 1). The precipitate at pH=8.6 was mainly amorphous iron oxide, of which size ranged from 2 to 10 nm and mainly consisting of Fe, O, and Si (step 2). At pH=9.5, nesquehonite [$Mg(HCO_3)(OH){\cdot}2(H_2O)$] and lasfordite [$MgCO_3{\cdot}H_2O$] were formed after reaction with $CO_2$ (step 3). The size of carbonated minerals was ranged from 1 to $6{\mu}m$. These results indicated that the acid treatment of serpentine and pH swing processes for the serpentine can be used for synthesis of other materials such as silica, iron oxides and magnesium carbonate. Also, This process may be useful for the precursor synthesis and $CO_2$ sequestration via mineral carbonation.

• Korean Journal of Applied Biomechanics
• /
• v.22 no.4
• /
• pp.421-428
• /
• 2012

The purpose of this study was to verify the effects of developed assisting wear which maximize trunk(back) muscle's stretch-shortening effect during backswing and downswing for increasing golf ball carrying distance. Design and fabrication of assistive wear were performed based on the results of analyzed data of trunk EMG activity from the golf drive swings of elite professional male golfers during back swing and downswing phases. After the prototype of wear was produced, surface EMG and Flight scope tests were conducted to verify the effectiveness of the wear for increasing distance to the professional golfers. Results indicated that wearing trial showed significant longer carry distance than the non-wearing trial(p<.001). The carry distance of wearing trial showed an average 229 m compared to the non-wearing trial, the average 225 m. The swing with wearing also produced significantly faster ball speed than the trial without wearing(p<.05). Average 245 Km/h and 244 Km/h were produced for the swing with and without wearing trails, respectively. EMG results also indicated that the muscle activity of left psoas was significantly increased for wearing trial during downswing and near the impact. Thus, this may affect positively to increase club head speed. The activity of the left latissimus dorsi was dramatically increased during the final stage of swing. This generates elongation effect for longer follow-through and increased impulse between club and ball so eventually valid assistance to increase carry distance. Therefore, the developed assisting wear was proved to be effective tool for increasing golf ball carry distance with maximizing trunk(back) muscle's stretch-shortening effect during backswing and downswing.

• KSBB Journal
• /
• v.16 no.2
• /
• pp.207-211
• /
• 2001

Statistical experimental design methods were employed to select the cultivation factors influencing latic acid production during the fermentation of kitchen refuses. Working volume and pH swings were identified as the main factors affecting lactic acid production. Optimum pH swing was pH 7.8 and working volume was 125 mL in a 250 mL flask. Under optimum condition, lactic acid was produced at 21.8 g/L, which was 6.2 times higher than produced during uncontrolled fermentation.

• Clean Technology
• /
• v.25 no.4
• /
• pp.311-315
• /
• 2019

The cation extraction and impurity separation were studied in order to investigate the recyclability of a slag produced from the steel refinery industry. Two types of slag (Slag-A, B) were collected and characterized in this study. The initial characterization by X-ray diffraction (XRD) and X-ray fluorescence (XRF) confirmed the existence of various kinds of ions in the slag such as Ca²⁺ (30 ~ 40%), Fe³⁺ (20 ~ 30%), Si⁴⁺ (15%), Al³⁺ (10%), Mn²⁺ (7%), and Mg²⁺ (3 ~ 5%). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis on the extracted slag using 2 M HCl as a solvent indicated that a higher concentration of Ca²⁺ was extracted as the S/L ratio was increased. The Ca²⁺ extraction concentration were found to be 8,940 mg L^-1 (Slag-A) and 10,690 (Slag-B) mg L^-1 when the S/L ratio for Ca²⁺ extraction was 0.1. However, the extract was strongly acidic ( < pH 1) at 0.1 S/L. Also the other ions (impurities) were extracted simultaneously in addition to Ca²⁺. To increase the purity of Ca²⁺ in order to transform the slag to a high value resource, a pH-swing was conducted. The impurities tended to precipitate at higher rate as the pH was increased. Notably, the Ca²⁺ rapidly precipitated above a certain pH and at a pH of 10.5, while the selectivity of Ca²⁺ was over 99%. It is expected that the aqueous solution in which high contents of Ca²⁺ was selectively dissolved in this study would be suitable for the carbonation process for reducing CO₂ and for the production of calcium carbonate.

• Korean Journal of Applied Biomechanics
• /
• v.15 no.1
• /
• pp.75-89
• /
• 2005

D. K. LEE, J. S. LEE, B. J. LEE, H. S. LEE, Y. J. KIM, S. B. PARK, J. P. JOO. Plantar foot pressure analysis during golf swing motion using plantar foot pressure measurement system. Korean Journal of Sport Biomechanics, Vol. 15, No. 1, pp. 75-89, 2005. In this study, weight carrying pattern analysis and comparison method of four foot region were suggested. We used three types of club(driver, iron7, pitching wedge). This analysis method can compare between top class golfer and beginner. And the comparison data can be used to correct the swing pose of trainee. If motion analysis system, which can measure the swing speed and instantaneous acceleration at the point of hitting a ball, is combined with this plantar foot force analysis method, new design development of golf shoes to increase comfort and ball flight distance will be available. 1. Address acting, forces concentrated in rare foot regions and lateral foot of right foot. Back swing top acting, relatively high force occurred in medial forefoot region of left foot and forefoot region of right foot. Impact acting, high force value observed in the lateral rarefoot region of left foot and medial forefoot region of right foot. Finish acting, force concentration observed on the lateral region and rarefoot region of left foot. 2. Forces were increased in address of right foot with clubs length increased. All clubs, back swing top acting, high force value observed in the lateral forefoot region of right foot. All clubs, in impact, high force value observed in the lateral rarefoot region of left foot and medial forefoot region of right foot. Finish acting, force concentration observed on the rarefoot region in driver and lateral foot region in iron on left foot. 3. Right foot forces distribution were increased in address, back swing top and left foot force distribution were increased in impact, finnish