Bis (2-ethylhexyl)phosphoric acid (HDEHP) is a renowned extractant, favored for its affinity to selectively remove uranium via its P=O groups. We previously synthesized HDEHP-functionalized mesoporous silica microspheres for solid-phase uranium adsorption. Herein, we investigated the kinetic and isothermal behavior of uranyl ion adsorption in mesoporous silica microspheres functionalized with phosphate groups. Adsorption experiments were conducted by equilibrating 20 mg of silica samples with 50 mL of uranium solutions, with concentrations ranging from 10 to 100 mgU L−1 for isotherms and 100 mgU L−1 for kinetics. Three distinct samples were prepared with varying HDEHP to TEOS molar ratios (x = 0.16 and 0.24) and underwent hydrothermal treatment at different temperatures, resulting in distinct textural properties. Contact times spanned from 1 to 120 hours. For x = 0.16 samples, it took around 50 and 11 hours to reach equilibrium for the hydrothermally treated samples at 343 K and 373 K, respectively. Adsorbed quantities were similar (99 and 101 mg g-1, respectively), indicating consistent functional group content. This suggests that the key factor influencing uranium adsorption kinetics is pore size of the silica. The sample treated at 373 K, with a larger pore size (22.7 nm) compared to 343 K (11.5 nm), experienced less steric hindrance, allowing uranium species to diffuse more easily through the mesopores. The data confirmed the excellent fit of pseudo-second-order kinetic model (R2 > 0.999) and closely matched the experimental value, suggesting that chemisorption governs the rate-controlling step. To gain further insights into uranium adsorption behavior, we conducted an adsorption isotherm analysis at various initial concentrations under a constant pH of 4. Both the Langmuir and Freundlich isotherm models were applied, with the Langmuir model providing a superior fit. The relatively high R2 value indicated its effectiveness in describing the adsorption process, suggesting homogenous sorbate adsorption on an energetically uniform adsorbent surface via a monolayer adsorption and constant adsorption site density, without any interaction between adsorbates on adjacent sites. Remarkably, differences in surface area did not significantly impact uranium removal efficiency. This observation strongly suggests that the adsorption capacity is primarily governed by the loading amount of HDEHP and the inner-sphere complexation with the phosphoryl group (O=P). Our silica composite exhibited an impressive adsorption capacity of 133 mg g-1, surpassing the results reported in the majority of other silica literature.

In this study, we evaluated the performance of phosphate-functionalized silica in adsorbing uranium and provided insights into optimizing the initial conditions of the uranium solution (concentration and pH), which are often overlooked in uranium adsorption studies. While most studies take into account the effect of pH on both the surface charge of the adsorbents and the dissolved speciation of uranium in solution, they often overlook the formation of solid phases such as β-UO2(OH)2 (cr) and UO3· 2H2O(cr), leading to an overestimation of the adsorption capacity. To address this issue, we considered the speciation of U(VI) calculated using thermodynamic data. Our findings suggest that it is reasonable to evaluate the adsorption performance at pH 4 and concentration below 1.35 mM. The formation of β-UO2(OH)2 (cr) starts at 23 μM (pH 5) and 1 μM (pH 6) and increases sharply with increasing concentration. To avoid interference from the formation of solid phases, experiments should be conducted at lower concentrations, which in turn require very small msorbent/Vsolution ratios. However, controlling small amounts of sorbent can be challenging, and increasing the volume of the solution can generate significant amounts of radioactive waste. We also used UV-vis spectra analysis to investigate the formation of solid phases. We found that a 100 mg L-1 uranium solution resulted in the formation of colloidal particles in the solid phase after 2.5 hours at pH 6, while at pH 4, no significant changes in absorbance were observed over 120 hours, indicating a stable ion phase. Based on these conditions, we obtained an excellent adsorption capacity of 110 mg g-1.

The objective of this study is to estimate the mechanical characteristics and nonlinear behaviors on the geometric nonlinear analysis of curved cable-membrane roof systems for long span lightweight roof structures. The weight of a cable-membrane roof dramatically can reduce, but the single layer cable-membrane roof systems are too flexible and difficult to achieve the required structural stiffness. A curved cable roof system with reverse curvature works more effectively as a load bearing system, the pretension of cables can easily increase the structural stiffness. The curved cable roof system can transmit vertical loads in up and downward direction, and work effectively as a load bearing structure to resists self-weights, snow and wind loads. The nonlinear behavior and mechanical characteristics of a cable roof system has greatly an affect by the sag and pretension. This paper is carried out analyzing and comparing the tensile forces and deflection of curved roof systems by vertical loads. The elements for analysis uses a tension only cable element and a triangular membrane element with 3 degree of freedom in each node. The authors will show that the curved cable-membrane roof system with reverse curvature is a very lightweight and small deformation roof for external loads.

In this study, we applied a membrane distillation process to investigate a feasibility of treating a wastewater with high concentration of organic matters including nitrogen and phosphorus. The laboratory scale experiment was performed by using a hydrophobic PVDF membrane with the pore size of 0.22 μm and porosity of 75%. The installation was direct contact type where the temperature difference between a feed and permeate side was controlled to have a range from 20 to 60°C. We observed a flux variation and a concentration changes of COD, PO4 3-－P, NH4 + -N and conductivity of feed side as well as permeate side with various temperature differences (20 to 60°C), cross flow velocities (0.09 to 0.27 m/s) through the module, and pH (6.6 to 12.0) of the feed that has the initial concentration of COD about 1,000 mg/L, total nitrogen 390 mg/L, total phosphorus 10 mg/L, conductivity of 7,000 μs/cm. The results showed that the average flux was ranged from 4 to 40 L/m2/hr which was almost similar with the flux of NaCl and deionized water used as a feed solution. The lowest flux was obtained at the operating condition with the temperature difference of 20°C and cross flow velocity of 0.09 m/s while the highest one was measured with 60°C and 0.27 m/s. Above 99% of COD and PO4 3- -P in the feed could be rejected regardless of an operating condition. However, the removal rate of ammonium nitrogen was varied from 64 to 99% depending on the pH of feed solution.

The performance of the new aerobic digestion system combined with inorganic sludge separation unit and sludge solubilization unit, CaviTec II, is evaluated. Anaerobic digester effluent sludge is used for feed sludge of CaviTec II system. By addition of CaviTec II, the amount of cake generated is reduced by 27%, and the soluble nitrogen is reduced by 92%.

The performance of inorganic sludge separation system is evaluated. Anaerobic digester effluent sludge is used for feed sludge of this system and hydrocyclone is used for inorganic sludge separation. For phosphorus removal and recovery MgCl2 is pumped into MAP growth tank, a component of inorganic sludge separation system. Using this system inorganic sludge which contained less than 40 % of organic matter can be discharged stably and the maximum amount of separated inorganic sludge is 13.4 % of influent sludge based on dry solid. The amount of phosphorus recovered as MAP(as P) is 16.7 % to influent T-P.

This study was performed to assess the current stock condition of elkhorn sculpin along the Uljin area in the East Sea of Korea. To assess the state of the stock, yield-per-recruit (YPR) and spawning biomass-perrecruit (SBPR) analyses were performed. Estimates of Fmax and F0.1 were 2.10/year and 0.48/year, respectively, and those of F35% and F40% were 0.66/year and 0.54/year, respectively. Current fishing mortality was estimated at 0.63/year and the current age at first capture was 2.41years. F40% was set as the target reference point of the stock. SBPR at F40% and current SBPR were estimated to be 41.85g and 37.77g, respectively. Estimated FOTY which is the fishing mortality for the overfished threshold yield was 0.49/year. The ratio of SBPR/SBPRMSY was calculated as 0.90 and that of F/FOTY was 1.05. The ratio of tc/tc opt was calculated as 1.15 and that of F/FOTY was 1.17. Therefore, the current stock condition of elkhorn sculpin along the Uljin area of Korea has not been overfished, however, it indicates that a light overfishing is going on this stock.

최근 First Person Shooter (FPS) 게임 시장에서 ‘플래닛 사이드 2’ 를 비롯한 대규모 온라인 FPS (MMOFPS: Massively Multi-player Online FPS) 장르가 주목받고 있다. 수백 또는 수천 명이 접속하는 게임 서버에서 네트워크 부하를 경감시키기 위해서 널리 사용되는 방법 중 하나 는 데드레커닝이다. 본 논문에서는 MMOFPS 게임을 위한 데드레커닝 구현 시 주요 캐릭터 상 태 갱신 변수 중 하나인 방향에 대하여 효율적으로 허용 임계각을 계산하는 수학적 방법을 제 안한다. 제안하는 방법은 게임사용자들을 대상으로 하는 수행 실험을 통해 움직임 오차를 최소 화하며 자유스러운 방향 갱신에 대한 효율성을 검증 하였다

실내조경용 화분에서 사용되는 관수방법별 배지의 수분분포 및 심지종류별 수분흡수 특성을 구명하였다. 심지 종류는 극세사, 관수용 부직포, 면제품 그리고 관수방법은 물뿌리개, 점적핀, 그리고 심지 관수로 처리하였다. 관수용 심지 3종류의 수분흡수 높이는 제품 간에 큰 차이가 있었으나, 배지로 이동되는 수분 공급 높이는 15일 동안 약 20 cm로 처리 간에 차이가 없었다. 또한 심지의 수분 흡수속도는 초기 30분 동안(약 20 cm 높이) 빠른 속도로 흡수된 후 느려지는 특성을 보였다. 관수용 심지는 1차, 2차 흡수지대로 구분되며 1차 흡수지대는 심지가 침지된 물에 의해 직접 흡수되며 흡수속도가 빨랐다. 2차 흡수지대는 1차 흡수지대에 의해 공급된 배지의 물이 공급원이 되어 다시 심지에 흡수되는 곳으로, 흡수 속도가 느리고 흡수된 후 배양토로 이동이 어려운 것으로 보인다. 물뿌리개를 이용한 관수는 많은 물이 짧은 시간에 수평으로 공급되지만 점적관수의 경우 원형으로 공급되고(Snyder 1990) 심지관수의 경우에는 천천히 적은 물이 옆으로 공급되는 특성을 나타낸다. 결과적으로 관수용 심지는 재질에 관계없이 배양토 높이 약 15 cm까지가 수분 공급이 가장 원활히 이루어지며, 높이 약 20 cm에 수분 이용한계선이 존재한다. 또한 건물내에 식물의 증발산양이 적은 곳에서 사용되는 미세관수에는 심지 관수방법이 적합한 것으로 보인다.