Sungwon Park

CO2 capture from simulated fuel gas mixtures using semiclathrate hydrates formed by quaternary ammonium salts.

In order to investigate the feasibility of semiclathrate hydrate-based precombustion CO2 capture, thermodynamic, kinetic, and spectroscopic studies were undertaken on the semiclathrate hydrates formed from a fuel gas mixture of H2 (60%) + CO2 (40%) in the presence of quaternary ammonium salts (QASs) such as tetra-n-butylammonium bromide (TBAB) and fluoride (TBAF). The inclusion of QASs demonstrated significantly stabilized hydrate dissociation conditions. This effect was greater for TBAF than TBAB. However, due to the presence of dodecahedral cages that are partially filled with water molecules, TBAF showed a relatively lower gas uptake than TBAB. From the stability condition measurements and compositional analyses, it was found that with only one step of semiclathrate hydrate formation with the fuel gas mixture from the IGCC plants, 95% CO2 can be enriched in the semiclathrate hydrate phase at room temperature. The enclathration of both CO2 and H2 in the cages of the QAS semiclathrate hydrates and the structural transition that results from the inclusion of QASs were confirmed through Raman and (1)H NMR measurements. The experimental results obtained in this study provide the physicochemical background required for understanding selective partitioning and distributions of guest gases in the QAS semiclathrate hydrates and for investigating the feasibility of a semiclathrate hydrate-based precombustion CO2 capture process.

Thermodynamic and Spectroscopic Identification of Guest Gas Enclathration in the Double Tetra-n-butylammonium Fluoride Semiclathrates

The precise nature and unique pattern of the double tetra-n-butylammonium fluoride (TBAF) semiclathrates with a guest gas (CH(4) or CO(2)) was closely investigated through thermodynamic and spectroscopic analyses. The three-phase equilibria of semiclathrate (H), liquid water (L(W)), and vapor (V) for the ternary CH(4) + TBAF + water and CO(2) + TBAF + water mixtures with various TBAF concentrations were experimentally measured in order to determine the stability conditions of the double TBAF semiclathrates. The double CH(4) (or CO(2)) + TBAF semiclathrates showed remarkably enhanced thermal stability when compared with pure CH(4) (or CO(2)) hydrate. The highest stabilization effect was observed at the stoichiometric concentration of pure TBAF semiclathrate, which is 3.3 mol %. Gas uptake measurements were undertaken in order to estimate the amount of gas consumed during double semiclathrate formation. CH(4) was found to be a relatively more favorable guest for the 5(12) cages of the double TBAF semiclathrate than CO(2). From the results of the NMR and Raman spectroscopic analyses it was identified that the guest gas molecules (CH(4) or CO(2)) were enclathrated in the 5(12) cages of the double TBAF semiclathrates. The overall results given in this study are useful for understanding the fundamental guest gas enclathration behavior in the double semiclathrates.

2-Propanol as a co-guest of structure II hydrates in the presence of help gases.

The enclathration of 2-propanol (2-PrOH) as a co-guest of structure II (sII) hydrates in the presence of CH4 and CO2 was experimentally verified with a focus on macroscopic phase behaviors and microscopic analytical methods such as powder X-ray diffraction (PXRD) and NMR spectroscopy. 2-PrOH functioned as a hydrate promoter in the CH4 + 2-PrOH systems, whereas it functioned as an apparent hydrate inhibitor in the CO2 + 2-PrOH systems despite the inclusion of 2-PrOH in the hydrate lattices. From the PXRD patterns, both double CH4 + 2-PrOH and double CO2 + 2-PrOH hydrates were identified to be cubic (Fd3m) sII hydrates. From the (13)C NMR spectra, it was found that, at a lower 2-PrOH concentration, the small 5(12) cages of the sII hydrate were occupied by CH4 molecules only, whereas the large 5(12)6(4) cages were shared by CH4 and 2-PrOH molecules. However, at a stoichiometric concentration, the large cages were occupied by 2-PrOH molecules only, and the corresponding chemical formula for this concentration is 1.50CH4·0.98 2-PrOH·17H2O.

Structural transformation of isopropylamine semiclathrate hydrates in the presence of methane as a coguest

Guest-induced structural transformation in amine semiclathrate hydrates is a unique pattern caused by modifying the hydrophobic-hydrophilic balance, and thus, it can be applied to potential gas storage and transportation areas. The experimental results of the structural transformation of isopropylamine (IPA) semiclathrate hydrates in the presence of methane (CH(4)) as a coguest are presented with a focus on the macroscopic phase behavior and microscopic analytical methods such as powder X-ray diffraction (PXRD) and NMR spectroscopy. The introduction of CH(4) molecules as coguests changed the structure of the IPA·8.0H(2)O semiclathrate hydrates (hexagonal, P6(3)/mmc) to sII gas hydrates (cubic, Fd3m). The microscopic analysis results indicate that the guest gas distribution and the clathrate hydrate composition can be altered with adjustment of the IPA concentration. The overall experimental results are valuable for increased understanding of the stability conditions, structural details, and guest-host interactions in hydrophobic guest gas + IPA clathrate hydrates.

SGSim: A unified smart grid simulator

SGSim is a unified simulator to enable development and evaluation of new operation algorithms and technologies for smart grids. SGSim provides full-scale distribution side virtual environment that smart grid is pursuing by combining power flow and communication altogether. Essential elements such as customers, intelligent electronic devices, and renewable resources, are designed as agent models and they interact and communicate with each other or with operation systems. In addition, to consider the regional characteristics of renewable generations weather simulation is combined. It has a multi-agent and multi-platform architecture for scalability and flexibility. With the simulation system, unexpected impact hidden behind complex correlations and influence propagation for specific events can be easily monitored and evaluated.

Clinical and pathologic evaluation of patients with prostate cancer and colorectal cancer five or more years after curative resection

The survival of men diagnosed with colorectal cancer (CRC) has improved over time, and the current 5‐year overall survival rate is 65.1 per cent. The long survival of patients with CRC raises issues regarding risk of a second primary prostate cancer and the need for continued proper surveillance. The aim of the study was to evaluate the incidence of prostate cancer in a uniform CRC population.

Factors affecting the difficulty of laparoscopic total mesorectal excision for mid- to lower rectal cancer

SummaryBackgroundThe purpose of this study was to evaluate the predictive value of clinical and anatomical features on magnetic resonance imaging (MRI) that can affect pelvic dissection time for treating mid- to lower rectal cancer.MethodsA total of 90 consecutive male patients who underwent total mesorectal excision for mid- to lower rectal cancer were retrospectively assessed. MRI pelvimetry data were analyzed to identify anatomical features that could affect pelvic dissection time.ResultsUnivariate analysis indicated that tumor distance from the anal verge (p = 0.001), preoperative chemoradiotherapy (p  = 0.002), and interspinous distance (p = 0.002) were significantly associated with pelvic dissection time.ConclusionPatients with a short interspinous distance may require a longer pelvic dissection time for treating rectal cancer by resection.

An Irradiation Prediction Model for Photovoltaic Power Generations Under Limited Weather Information

Abstract The customer side operation is getting more complex and difficult in a smart grid environment because of the adoption of renewable resources, such as photovoltaic, wind turbine, geothermal and fuel cell and the use of energy storage systems. In performing energy management planning or scheduling, it is essential to forecast non-controllable resources accurately and robustly. Photovoltaic is one of the common renewable energy resources in customer side. The output of photovoltaic is directly related to insolation and temperature at the installed location for a specific time. Therefore, obtaining precise weather information is critical for accurate estimation. However, the weather forecast information that customers can access is usually not precise and even not quantitative. In this paper, an irradiation prediction model for photovoltaic power generations based on limited weather forecast information is proposed. It is assumed that customers can obtain only ordinary daily weather forecast that usually provides the qualitative prediction of 3 hours unit for the next 24 or 48 hours. Some existing insolation estimation methods are combined and power conditioning system characteristics are considered. The model is applied to a field test site, and verified with historic data.