The Green tensor of Mindlin's anisotropic first strain gradient elasticity

We derive the Green tensor of Mindlin's anisotropic first strain gradient elasticity. The Green tensor is valid for arbitrary anisotropic materials, with up to 21 elastic constants and 171 gradient elastic constants in the general case of triclinic media. In contrast to its classical counterpart, the Green tensor is non-singular at the origin, and it converges to the classical tensor a few characteristic lengths away from the origin. Therefore, the Green tensor of Mindlin's first strain gradient elasticity can be regarded as a physical regularization of the classical anisotropic Green tensor. The isotropic Green tensor and other special cases are recovered as particular instances of the general anisotropic result. The Green tensor is implemented numerically and applied to the Kelvin problem with elastic constants determined from interatomic potentials. Results are compared to molecular statics calculations carried out with the same potentials

Diffuse-interface polycrystal plasticity: Expressing grain boundaries as geometrically necessary dislocations

The standard way of modeling plasticity in polycrystals is by using the crystal plasticity model for single crystals in each grain, and imposing suitable traction and slip boundary conditions across grain boundaries. In this fashion, the system is modeled as a collection of boundary-value problems with matching boundary conditions. In this paper, we develop a diffuse-interface crystal plasticity model for polycrystalline materials that results in a single boundary-value problem with a single crystal as the reference configuration. Using a multiplicative decomposition of the deformation gradient into lattice and plastic parts, i.e. F(X,t) = F^L(X,t) F^P(X,t), an initial stress-free polycrystal is constructed by imposing F^L to be a piecewise constant rotation field R^0(X), and F^P = R^0(X)^T, thereby having F(X,0) = I, and zero elastic strain. This model serves as a precursor to higher order crystal plasticity models with grain boundary energy and evolution.Comment: 18 pages, 7 figure

Penerapan Muqhata’ah dalam Meningkatkan Hafalan Qur’an pada Siswa Kelas VIII di Ma’had An-Nikmah Al-Islamiyah Phnom Penh Cambodia

Artikel ini membahas tentang problematika sebagian penghafal al-Qur’an adalah lupanya hafalan dari ingatan karena mengejar kuantitas. Dengan demikian, untuk memperoleh hafalan yang kuat membutuhkan metode tertentu dalam menghafalnya. Metode penelitian yang digunakan adalah kualitatif lapangan (field research) yaitu penelitian yang mengharuskan peneliti berangkat ke “lapangan? untuk mengadakan pengamatan tentang sesuatu fenomena dalam suatu pendidikan. Adapun hasil dari penelitian ini adalah media yang digunakan mudah difahami. Serta semangat para siswi dalam menghafal al-qur’an yang sangat tinggi dan juga bantuan dari teman-teman asramanya untuk menyimak hafalan siswi atau memuroja’ahkan hafalan siswi. Adapun tujuan dari penelitian ini adalah untuk mengetahui bagaimana penerapan metode Muqhata’ah dalam meningkatkan hafalan qur’an Siswi kelas VIII di An-Nikmah Al-Islamiyah, untuk mengetahui faktor keberhasilan dan kelemahan penerapan metode Muqhata’ah dalam pembelajaran Al-Qur’an. Faktor penghambat penerapan metode ini ialah kosentrasi siswi yang masih susah dikendalikan

Statistics of grain microstructure evolution under anisotropic grain boundary energies and mobilities using threshold-dynamics

This paper investigates the statistical behavior of two-dimensional grain microstructures during grain growth under anisotropic grain boundary characters. We employ the threshold-dynamics method, which allows for unparalleled computational speed, to simulate the full-field curvature motion of grain boundaries in a large polycrystal ensemble. Two sets of numerical experiments are performed to explore the effect of grain boundary anisotropy on the evolution of microstructure features. In the first experiment, we focus on abnormal grain growth and find that grain boundary anisotropy introduces a statistical preference for certain grain orientations. This leads to changes in the overall grain size distribution from the isotropic case. In the second experiment, we examine the texture development and growth of twin grain boundaries at different initial microstructures. We find that both phenomena are more pronounced when the initial microstructure has a dominant fraction of high-angle grain boundaries. Our results suggest effective grain boundary engineering strategies for improving material properties.Comment: 25pages, Figure

Malpraktik Medik Ditinjau dari Aspek Pertanggungjawaban Hukum Perdata

Malpraktik adalah istilah umum dan mempunyai konotasi yang berpengertian hukum, berupa pelanggaran hukum oleh seorang dokter melakukan praktik kedokteran, pelanggaran yang menimbulkan kerugian pada pihak ketiga. Tuntutan masyarakat untuk membawa kasus dugaan malpraktik medik ke pengadilan dapat dipahami mengingat sangat sedikit jumlah kasus malpraktik medik yang diselesaikan di pengadilan. Akan tetapi masyarakat sering beranggapan keliru bahwa tindakan medis yang menimbulkan kerugian dapat dikategorikan sebagai malpraktik medis. Berdasarkan uraian di atas maka permasalahan yang dapat dikemukakan dalam penulisan ini adalah: (1) Bagaimana malpraktik medik oleh dokter terhadap pasien ditinjau dari aspek pertanggung jawaban hukum perdata ? (2) Bagaimana cara penyelesaian secara perdata apabila terjadi kasus malpraktik medik di Pengadilan Negeri Semarang? Metode pendekatan dalam penelitian ini adalah metode pendekatan secara Yuridis Sosiologis atau Social Legal Approach, spesifikasi penelitian yang sifatnya “Deskriptif analitis. Metode analisis data atau pengolahan data yang telah masuk dengan mempergunakan metode “induktif kualitatif” Hasil penelitian menunjukkan bahwa (1) Malpraktik medik oleh dokter terhadap pasien ditinjau dari aspek pertanggung jawaban hukum perdata harus ada relevansi dengan perbuatan melanggar hukum Pasal 1364 dan Pasal 1366 KUH Perdata, yaitu pertama pasien harus mengalami suatu kerugian, kedua ada kesalahan atau kelalaian, ketiga ada hubungan kausal antara kerugian dan kesalahan dan keempat perbuatan itu melanggar hukum (2) Cara penyelesaian secara perdata apabila terjadi kasus malpraktik medik di Pengadilan Negeri Semarang, sebelum dilakukan sidang terlebih dahulu diupayakan mediasi antara kedua belah pihak yang bersengketa, apabila tidak dapat ditemukan penyelesaiannya maka tindakan selanjutnya adalah melakukan tuntutan di Pengadilan Negeri Semarang dengan mengajukan pembuktian, selama ini kasus Malpraktik medik di Pengadilan Negeri Semarang dilaksanakan melalui mediasi antara lain dengan Alternative Dispuit Resolution. Kata Kunci : Malpraktik, Dokter, KUHPerdat

Results on the interaction between atomistic and continuum models

University of Minnesota Ph.D. dissertation. August 2014. Major: Aerospace Engineering and Mechanics. Advisor: Ellad B. Tadmor. 1 computer file (PDF); v, 108 pages, appendix A.In this thesis, we develop continuum notions for atomistic systems which play an important role in developing accurate constitutive relations for continuum models, and robust multiscale methods for studying systems with multiple length and time scales. We use a unified framework to study the Irving--Kirkwood and Murdoch--Hardy procedures used to obtain definitions for continuum fields in atomistic systems. We identify and investigate the following three problems. 1. Continuum fields derived for atomistic systems using the Irving--Kirkwood or the Murdoch--Hardy procedures correspond to a spatial description. Due to the absence of a deformation mapping field in atomistic simulations, it is uncommon to define atomistic fields in the reference configuration. We show that the Murdoch--Hardy procedure can be modified to obtain pointwise continuum fields in the reference configuration using the motion of particles as a surrogate for the deformation mapping. In particular, we obtain definitions for the first and second atomistic Piola--Kirchhoff stress tensors. An interesting feature of the atomistic first Piola--Kirchhoff stress tensor is the absence of a kinetic contribution, which in the atomistic Cauchy stress tensor accounts for thermal fluctuations. We show that this effect is also included in the atomistic first Piola--Kirchhoff stress tensor through the motion of the particles. 2. We investigate the non-uniqueness of the atomistic stress tensor stemming from the non-uniqueness of the potential energy representation. In particular, we show using rigidity theory that the distribution associated with the potential part of the atomistic stress tensor can be decomposed into an irrotational part that is independent of the potential energy representation, and a traction-free solenoidal part. Therefore, we have identified for the atomistic stress tensor a discrete analog of the continuum generalized Beltrami representation (a version of the vector Helmholtz decomposition for symmetric tensors). 3. We show that an ambiguity in the original Irving--Kirkwood procedure resulting due to the non-uniqueness of the energy decomposition between particles can be completely avoided through an alternate derivation for the energy balance. It is found that the expressions for the specific internal energy and the heat flux obtained through the alternate derivation are quite different from the original Irving--Kirkwood procedure and appear to be more physically reasonable. Next, we apply spatial averaging to the pointwise field to obtain the corresponding macroscopic quantities. These lead to expressions suitable for computation in molecular dynamics simulations