Akira Takada

... 6 Ramaswamy, V.; Boucher, O.; Haigh, J.; Hauglustaine, D.; Haywood, J.; Myhre, G.; Nakajima, T.; Shi, GY ... 9 Wallington, TJ; Schneider, WF; Sehested, J.; Bilde, M.; Platz, J.; Nielsen, OJ; Christensen, LK; Molina, MJ; Molina, LT; Wooldridge, PW J Phys Chem A 1997, 101, 8264. ...

ABSTRACT The intermolecular interaction energies of the CX3OCHO dimers, CX3OCHO–n(H2O), and CX3OCHO–n(HO2) (X=H,F; n=1,2) complexes are studied by using molecular orbital calculations at the (U)MP2/aug(df,pd)-6-311G**//(U)B3LYP/6-311G** level. We first confirmed the reliability of this level of calculation by utilizing examples of two complexes, CH3OCHO–HO2 (syn) and CF3OCHO–HO2 (syn). The calculated intermolecular interaction energies for the formate dimers (−3.75 to −5.19 kcal mol−1) and CX3OCHO–H2O (−2.39 to −4.90 kcal mol−1) are relatively small. On the other hand, the CX3OCHO–HO2 complexes have larger interaction energies (−4.78 to −9.69 kcal mol−1). The complexes, CX3OCHO–2(H2O) and CX3OCHO–2(HO2), have the largest intermolecular interaction energies (−12.42 to −13.89 kcal mol−1 and −14.47 to −18.39 kcal mol−1, respectively). Except for the formate dimer of syn–syn type, the interaction energies for the complexes with CF3OCHO are always smaller than the corresponding complexes with CH3OCHO. Finally, we estimated the concentrations of the complexes in the low and high water concentration conditions. In conclusion, it has been observed that the complexes studied in this work are not likely to form in the atmosphere.

ABSTRACT 学習精度の高くない学習機械(Weak Learner)を複数足し合わせることにより、相関性、予測性を向上させるアンサンブル学習法(Ensemble Learning)を回帰分析に適用するため、新しいアルゴリズムArcing_RAを提案した。モデルケースとしてFriedman Test; f(x) = 10sin(pix1x2) + 20(x2-0.5)2 + 10x4 + 5x5 + N(1,0) (x1-5は0-1のランダムな値；N(1,0)は正規分布で与えられる誤差)を用い、学習用に200データ、予測用に1000データを発生させ、相関、予測精度を評価した。学習機械としては、3層からなる階層型Neural Networkを用いた。1つのNeural Networkを用いた場合、中間層のNeuron数が10を越えると過学習が起こることが確認されたため、過学習の起こらない中間層に5個のNeuronを用いたNeural NetworkをWeak Learnerとして採用し、相関、予測精度が向上されるかテストを行った。各データの重みを決定するリサンプリングの方法が異なる3つの方法Arcing_RA1-3を検討した結果、いずれの方法も相関、予測における絶対平均誤差を約20%減少させることが確認され、その有効性が示された。

Molecular dynamics simulations of the swollen membrane of perfluorinated ionomer, which is composed of poly(tetrafluoroethylene) backbones and perfluosulfonic pendant side chains, have been undertaken to analyze the static and dynamic properties of the water and the side chain in the membrane. The calculations were carried out for four different water contents, 5, 10, 20 and 40 wt %, at 358.15 K and 0.1 MPa. The results are summarized as follows: (1) The sulfonic acid is the unique site to which water molecules can bind, and the other sites in the pendant side chain have no bound water even at high water concentration. (2) Sulfonic acids aggregate in the short range within 4.6-7.7 A despite the electrostatic repulsion between them. In such aggregates, a water molecule bridges two sulfonic acids. (3) Pendant side chains prefer to orient perpendicular to the hydrophilic/hydrophobic interface, and long-range correlation of side chain orientations is observed at 20 and 40 wt % water uptake membranes. (4) In a low water uptake membrane, the dynamics of water is substantially restricted due to strong attractive interactions with acidic sites. In contrast, at high water content, even the water locating near the sulfonic acid is relatively mobile. The short residence time of the bound water reveals that such water can frequently exchange position with relatively free water, which locates in the center of water cluster, in highly swollen membranes.

A comparison between water and methanol on the interaction with a pendant chain model for perfluorosulfonic ionomers (PFI), CF3OCF2CF2SO3−, was made by using molecular orbital calculation. Intermolecular interaction energy (Eint) of the most stable complex for CF3OCF2CF2SO3−+CH3OH, where methanol associates with sulfonic acid group, is −10.38kcal/mol at the MP2/aug-cc-pVDZ//B3LYP/6-31+G* level, and it is almost the same with that of CF3OCF2CF2SO3−+H2O complex (−10.58kcal/mol). Since an association of methanol to the sulfonic acid group is quite advantageous in energy, it is expected that, similarly to water, methanol would likely populate around the acidic site. On the contrary, according to a systematic Eint analysis for 500 random configurations, dissimilar distribution of Eint was observed for methanol compared with water. This is because methyl group substitution reduces oxygen surface area and causes more attractive dispersion energy with CF3OCF2CF2SO3− by about 1.0kcal/mol on average compared with water. To see how the difference in the interaction energy affects the solvation structure of methanol and water to the PFI, molecular dynamics simulations of a CF3OCF2CF2SO3− molecule in methanol solutions have also been carried out at the methanol concentration of 10–90mol%. Consequently, water probably associates with the sulfonic acid group-pushing methanol close to hydrophobic sites. It was also observed that methanol molecule tends to point its methyl group toward the solute at hydrophobic sites. These results demonstrated that methanol should locate in the vicinity of hydrophobic site compared with water due to methyl group substitution.

... 6 Ramaswamy, V.; Boucher, O.; Haigh, J.; Hauglustaine, D.; Haywood, J.; Myhre, G.; Nakajima, T.; Shi, GY ... 9 Wallington, TJ; Schneider, WF; Sehested, J.; Bilde, M.; Platz, J.; Nielsen, OJ; Christensen, LK; Molina, MJ; Molina, LT; Wooldridge, PW J Phys Chem A 1997, 101, 8264. ...