Impact response of thin-walled plane frame structures

A numerical study of the impact response of plane frame structures with thin-walled members was performed to predict the deformation and absorbed energy of automobiles under crash loading.The collapse characteristics of thin-walled members under axial compression or bending loads are considered in the present analysis. The load-displacement relations are given for curved beam members, and the inelastic deformations of members are described in terms of equivalent internal loads and their histories.Crash tests on simplified plane frame models impacted against a flat barrier were performed to verify the proposed method.Numerical analyses were also made of an oblique barrier impact of an automobile underframe structure and a rear end collision of a vehicle structural system. The analytical predictions were compared with the corresponding test results.     

Dynamic behaviour of thin cylindrical shells subjected to impulsive bending moments along their tips

The dynamic behaviour of thin cylindrical shells with concentrated masses at their tips is investigated when they are subjected to impulsive bending moments at their tips. The relationships between the dimensions of a cylinder, concentrated mass and maximum values of dynamic stresses are obtained. The fundamental equation of motion is solved by the Laplace transformation method. From the results of the theoretical analysis, it became evident that impulsive stresses become much larger than static ones. For the case where bending moments are applied statically, the fundamental equations are also derived, taking into account the effect of shearing force.     

Synthesis of Highly Oriented K(Ta,Nb)O3 (Ta:Nb = 65:35) Film Using Metal Alkoxides

Highly oriented K(Ta,Nb)O₃ (Ta:Nb = 65:35) (KTN) thin films of perovskite structure were synthesized successfully on Pt(100)/MgO(100) substrates from a metal alkoxide solution through reaction control. Homogeneous KTN coating solutions prepared from KOC₂H₅, Ta(OC₂H₅)₅, and Nb(OC₂H₅)₅ in ethanol were analyzed by ¹H, ¹³C, and ⁹³Nb NMR spectroscopy. The KTN precursor included a molecular-level mixture of K[M(OC₂H₅)₆] (M = Ta, Nb) units interacting in ethanol solution. X-ray pole figure measurement showed that perovskite KTN films crystallized on Pt(100)/MgO(100) substrates had not only a (100) orientation but also a three-dimensional regularity of grains. The remanent polarization and coercive field of the KTN film (thickness, 1.0 μm) crystallized at 700°C were 1.5 μC/cm² and 8.7 kV/cm, respectively, at 225 K.     

Chemical Processing and Microwave Characteristics of (Zr,Sn)TiO4 Microwave Dielectrics

Monosized spherical particles of (Zr, Sn)TiO₄ with an average diameter of about 0.3 μm were synthesized by the controlled hydrolysis of metal alkoxides. The as-prepared, amorphous, particles were compacted without any sintering aid, crystallized, and then sintered at 1600°C for 3 h into bodies with >96.0% of theoretical density. The dense sintered bodies of (Zr_0.80Sn_0.20)TiO₄ showed good microwave characteristics; ɛ_r= 40.0, Q = 5000, and τ_t= 3 ppm/°C at 10 GHz. The dielectric constant was remarkably dependent upon the relative densities of the sintered bodies and the change of the lattice parameters, while Q value was mainly affected by the oxygen deficiency. An increase of the dielectric constant with the substitution of Sn⁴⁺ in ZrTiO₄ was attributable to the enhancement of ionic polarization with the increase of the c -axis length.     

Incidence of nausea and vomiting after cholecystectomy performed via laparotomy or laparoscopy

Postoperative nausea and vomiting (PONV) are commonly observed adverse effects of general anesthesia. In a retrospective study of laparoscopy group (101 patient) and laparotomy group (101 patient), we evaluated the incidence of PONV after laparoscopic cholecystectomy. Most factors which could influence the incidence of PONV were not significantly different between the groups. The overall incidence of PONV during the first 17h postoperatively was 25.7% in laparoscopy group and 18.8% for laparotomy group respectively, but the risk was 3.2 times greater in laparoscopy group (15.8%) than in laparotomy group (5.0%) (P < 0.05) during the first postoperative hour. The risk of PONV was greater in laparoscopy group in female patients (23.4% versus 9.3% in laparotomy group, P < 0.05) and in obese patients (25.0% versus 0% in laparotomy group, P < 0.01) during the first postoperative hour. We conclude that laparoscopic cholecystectomy increases the incidence of PONV in early postoperative period probably by the effect of residual stretching and irritation of the peritoneum, and the risk is increased in female and obese patients.     

The electrical and optical properties of BiSiO2 cermet films

The electrical and optical properties of BiSiO₂ cermet films were studied. Using the temperature dependence of the resistivity of the cermet films and the dependence of the amount of oxidation of the fine bismuth particles on the volume percentage of bismuth, the three-dimensional percolation threshold composition was determined to be approximately 18 vol. % Bi.     

On the Sampling Distribution of Swap-Rate

When we are to select students using the result of an entrance examination, it is common to select N⁰ students out of N applicants on the basis of a composite score of m subtests, where N⁰, the number of students to be selected, is determined prior to the administration of the entrance examination. The swap-rate is an intuitively easy-tounderstand measure of the contribution of each subtest to the selection. The swap rate of the j-th test is defined as the proportion, to No, of the number of students who failed to pass the examination if the j-th test is not used for the selection.

In this paper we first discuss the sampling distribution of the swap-rate under the normality assumption and then show the result of a bootstrapping using real selection data.

     

Photopolymerization of methyl methacrylate initiated by a nitrogen ylide

The sensitization effect of 1-ethoxycarbonyliminopyridinium ylide (IPYY) on the photopolymerization was studied. Only acrylic monomers such as methyl methacrylate and methyl acrylate could be photoinitiated by IPYY, styrene being unaffected by the initiator employed. A free radical mechanism was confirmed by the kinetic study, the inhibiting effect of benzoquinone and the copolymer composition with styrene. Kinetic data suggested the formation of a complex between the IPYY and each monomer, which generates an initiating radical.     

膜孔中有线形接枝链的微囊的分子识别型控制释放特性研究

研制出了一种用于环境刺激感应控制释放的分子识别型微囊。该微囊具有核壳结构多孔膜，并在膜孔中接枝有作为分子识别开关的聚[异丙基丙烯酰胺－共－（苯并－18－冠－6－丙烯酰胺）]（poly(NIPAM0co-BCAm）线形链。采用了界面聚合法核壳结构多孔微囊膜，并采用了等离子体接枝填孔聚合法在膜孔内接枝poly(NIPAM-co-BCAm)线形链。囊内溶质从该微囊中的释放特性明显受环境溶液中Ba^2 离子的存在与否状态所控制。当环境溶液中没有BaCl2分子存在时，由于微囊膜孔内接枝的Poly(NIAM-co-BCAm）聚合物链呈收缩状态而使 开启，所以释放速度快，相反，当环境溶液中有BaCl2分子存在时，微囊膜孔内接枝的poly(NIPAM-co-BCAm）链呈膨胀状态，于是膜孔关闭，从而导致释放速度变得很慢，该具有poly(NIPAM-co-BCAm）接枝开关的微囊的分子识别刺激应释放特性显示出了良好的可逆性和可重复性。