Biphenyl-3,3′,4,4′-tetra­amine

The title compound, C12H14N4, has a crystallographically imposed centre of symmetry. Inter­molecular N—H⋯N hydrogen bonds between amino groups link adjacent mol­ecules into a three-dimensional network where ten-membered hydrogen-bonded rings are observed

2,4-Diamino-6-methyl-1,3,5-triazin-1-ium chloride

In the title compound, C4H8N5 +·Cl−, a two-dimensional layer packing network is observed in which every chloride anion links three adjacent 2,4-diamino-6-methyl-1,3,5-triazin-1-ium cations by N—H⋯Cl hydrogen-bonding inter­actions, forming 12-membered and eight-membered hydrogen-bonded rings with graph-set motifs R 4 4(12) and R 3 3(8), respectively. In addition, N—H⋯N hydrogen bonds are found between adjacent cations, forming another type of eight-membered [R 2 2(8)] hydrogen-bonded ring

2-Amino-6-nitro-1,3-benzothia­zol-3-ium hydrogen sulfate

In the title molecular salt, C7H6N3O2S+·HSO4 −, the 2-amino-6-nitro-1,3-benzothia­zole ring system is essentially planar [mean deviation = 0.0605 (4) Å]. In the crystal, N—H⋯O and O—H⋯O hydrogen-bonding inter­actions result in a layer motif

4-Amino­pyridinium azide 4-amino­pyridine solvate

In the title compound, C5H7N2 +·N3 −·C5H6N2, all N atoms of the azide anion are situated on a twofold rotational axis, so the 4-amino­pyridinium cation and 4-amino­pyridine mol­ecule, being related by symmetry, occupy one position in the asymmetric unit. Inter­molecular N—H⋯N hydrogen bonds generate a three-dimensional hydrogen-bonding network which consolidates the crystal packing

Incorporating A Learner Development Programme into A Self-access Centre in A University in Southern Taiwan

It has been pointed out that Taiwanese university students tend to be teacher dependent and not given enough opportunity to make decisions on their own learning when it comes to learning a foreign language (Chu, 2007; Cheng, 2006; Cheng, 2007; Cheng, 2008; Lin, 2009). Moreover, although more and more Taiwanese universities have established self-access centres, the facility is not widely used by students (Cheng 2008; Cheng 2007). This paper, therefore, proposes that integrating a learner development programme into a self-access centre in a Taiwanese university can be a solution to the issues mentioned above. This paper begins with an introduction of the main purposes of this paper and a description of Taiwanese university students in general. The second chapter reviews the literature on the concept of learner autonomy, reasons of promoting autonomy, the concept of learner development (or learner training, learning how to learn, etc.) and self-access centre. Following the literature review the third chapter gives an account of the context where this learner development programme is suggested to be implemented, the design of this programme and the rationales involved, the procedures of conducting this programme and the rationales involved and finally ends with a discussion on the anticipated problems and possible solutions to these problems. The concluding chapter suggests some implications for Taiwanese EFL teachers and language programme designers to consider

4,4′-(Cyclo­hexane-1,1-di­yl)dianilinium dichloride monohydrate

In the title compound, C18H24N2 2+·2Cl−·H2O, both the cation and the water mol­ecule lie on a twofold crystallographic axis. In the cation, the two benzene rings are perpendicular to each other, making a symmetry-constrained dihedral angle of 90°. In the crystal, N—H⋯Cl, O—H⋯Cl and N—H⋯O hydrogen bonds result in the formation of a three-dimensional network

Stress Solitary Waves Generated by a Second-Order Polynomial Constitutive Equation

In this paper, a nonlinear constitutive law and a curve fitting, two relationships between the stress-strain and the shear stress-strain for sandstone material were used to obtain a second-order polynomial constitutive equation. Based on the established polynomial constitutive equations and Newton's second law, a mathematical model of the non-homogeneous nonlinear wave equation under an external pressure was derived. The external pressure can be assumed as an impulse function to simulate a real earthquake source. A displacement response under nonlinear two-dimensional wave equation was determined by a numerical method and computer-aided software. The results show that a suit pressure in the sandstone generates the phenomenon of stress solitary waves