Sophia University

About: Sophia University is a education organization based out in Tokyo, Japan. It is known for research contribution in the topics: Nonlinear system & Catalysis. The organization has 4986 authors who have published 7657 publications receiving 106567 citations. The organization is also known as: Jōchi Daigaku.

Stress intensity factor analysis of interface cracks using X‐FEM

Abstract: The extended finite element method (X-FEM) proposed by Belytschko et al. (International Journal for Numerical Methods in Engineering 1999; 45: 602; 1999; 46: 131; 2001; 50: 993) uses interpolation functions based on the concept of partition of unity, and considers the asymptotic solution and the discontinuity of displacement fields near a crack independently of the finite element mesh. This paper describes the application of X-FEM to stress analyses of structures containing interface cracks between dissimilar materials. In X-FEM, an interface crack can be modelled by locally changing an interpolation function in the element near a crack. The energy release rate should be separated into individual stress intensity factors, K1 and K2, because the stress field around the interface crack has mixed modes coupled with mode-I and mode-II. For this purpose, various evaluation methods used in conjunction with numerical methods such as FEM and BEM are reviewed. These methods are examined in numerical examples of elastostatic analyses of structures containing interface cracks using X-FEM. The numerical results show that X-FEM is an effective method for performing stress analyses and evaluating stress intensity factors in problems related to bi-material fractures. Copyright © 2003 John Wiley & Sons, Ltd.

Molecular and Cellular Basis of Formation, Hardening, and Breakdown of the Egg Envelope in Fish

Abstract: Publisher Summary This chapter highlights some of the processes from formation to breakdown of the egg envelope (egg membrane) in fish from the perspective of cell and developmental biology The chapter describes the structure and functions of the egg envelope, compares the egg envelopes of various species, and deduces a biological concept of the egg envelope The chapter explores the egg envelope as a probe that can be used in the analysis of molecular, cellular, and developmental phenomena in living systems The egg envelope is an acellular structure enclosing the egg and embryo of all multicellular animals except sponges and some coelenterates The number of egg envelopes varies from one to several in different animal species Most of the egg envelopes in fish consist of two or three layers These layers are different in morphology, ultrastructure, stainability, and chemical properties The outer one or two layers are thin, while the innermost layer is usually the thickest The egg envelope of fish has been considered to be synthesized in oocytes or follicle cells and is classified as the primary or secondary egg envelope The envelopes of fertilized eggs of many fish are hard and tough structures with strong elasticity and are also insoluble in water The constituent proteins of the egg envelope are, therefore, inconvenient as immunogens to raise antibodies The hatching enzyme does not break down the egg envelope completely into free amino acids or small peptides but, by limited proteolysis, produces a mixture of water-soluble, high-molecular-weight glycoproteins

Poly(4-Vinylpyridine)-Based Interfacial Passivation to Enhance Voltage and Moisture Stability of Lead Halide Perovskite Solar Cells

Abstract: It is well known that the surface trap states and electronic disorders in the solution-processed CH3 NH3 PbI3 perovskite film affect the solar cell performance significantly and moisture sensitivity of photoactive perovskite material limits its practical applications. Herein, we show the surface modification of a perovskite film with a solution-processable hydrophobic polymer (poly(4-vinylpyridine), PVP), which passivates the undercoordinated lead (Pb) atoms (on the surface of perovskite) by its pyridine Lewis base side chains and thereby eliminates surface-trap states and non-radiative recombination. Moreover, it acts as an electron barrier between the perovskite and hole-transport layer (HTL) to reduce interfacial charge recombination, which led to improvement in open-circuit voltage (Voc ) by 120 to 160 mV whereas the standard cell fabricated in same conditions showed Voc as low as 0.9 V owing to dominating interfacial recombination processes. Consequently, the power conversion efficiency (PCE) increased by 3 to 5 % in the polymer-modified devices (PCE=15 %) with Voc more than 1.05 V and hysteresis-less J-V curves. Advantageously, hydrophobicity of the polymer chain was found to protect the perovskite surface from moisture and improved stability of the non-encapsulated cells, which retained their device performance up to 30 days of exposure to open atmosphere (50 % humidity).

Nearly perfect triplet-triplet energy transfer from Wannier excitons to naphthalene in organic-inorganic hybrid quantum-well materials.

Abstract: We report the observation of extremely efficient energy transfer (greater than 99%) in an organic-inorganic hybrid quantum-well structure consisting of perovskite-type lead bromide well layers and naphthalene-linked ammonium barrier layers. Time-resolved photoluminescence measurements confirm that the transfer is triplet-triplet Dexter-type energy transfer from Wannier excitons in the inorganic well to the triplet state of naphthalene molecules in the organic barrier. Using measurements in the 10-300 K temperature range, we also investigated the temperature dependence of the energy transfer.