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Résumé for Jakob Christensen
E-mail: info@jakobchr.com


Guest Researcher
Informatics and Mathematical Modeling, Lyngby, Denmark (2002-2004)
Object-oriented analysis, design and implementation in C++:
Completed the TRACMIX++ code with more than 50,000 lines of highly efficient C++ code for the numerical simulation of flow in large enclosures. Used the Portland Group Compiler suite under Linux.   Completed TRACMIX++ OO design using: Use Cases, CRC Cards, Class and Interaction Diagrams in UML (used ArgoUML under Linux);  Utilized OO design patterns frequently; Implemented TRACMIX++ with heavy use of STL, inheritance, templates, namespaces;  Developed library of 1-D functional classes (hierarchy) supporting a variety of mathematical operations;  Developed a design for solvers of non-linear equations using the strategy design pattern (secant method, Pegasus method);   Invented design pattern for classes of numerical methods with different order (=accuracy);  Invented design pattern for a completely flexible database storing physical properties of any number of fluids;   Developed flexible class for storing frequently used physical properties for optimal computational speed;  Developed a template based general 1-D computational grid with general 1-D grid elements;   Developed library of classes (hierarchy) describing flow source models;  Developed class hierarchy describing different flow paths;  MATLAB output generator: Developed a design for outputting any C++ class to a MATLAB .mat-file (ideal for doing post processing in MATLAB)
Mathematical/Numerical Modeling:

Derived a set of coupled non-linear PDEs describing fluid motion in large enclosures and   Derived discrete equations using a control volume approach for obtaining numerical solutions and   Derived the truncation errors associated with the discretizationConstructed discrete mathematical models for diffusion of heat and mass in a medium with discontinuities and  Derived the error associated with this discrete model;  Derived a mathematical model describing the pressure changes in a large enclosure and  Devised an algorithm suited for computing the pressure change;  Developed strategies for management of the large enclosure computational grid to ensure minimal computational cost with optimal accuracy
Computer simulations:
Ran computer simulations to verify/validate TRACMIX++.   Compared simulations to experimental data

Research Associate
Thermal-Hydraulics Group, Berkeley, California, USA (1997-2001)
TRACMIX++: Initial design of mathematical model, code design and implementation
Ran the Monte-Carlo code MCNP for nuclear reactor criticality studies
MATLAB code development:
Developed suite of m-scripts with about 5,000 lines of MATLAB code for simulating simpler flows in a large enclosure including scripts for post-processing;  Developed m-scripts for solving the transient 1-D multi-group neutron diffusion equation (a set of coupled PDEs, neutron kinetics including delayed neutrons) and  Solved the PDEs using the Method of Lines
Maple code development:
Developed Maple codes for obtaining analytical solutions to the PDEs describing transient heat and mass diffusion
Safety Assessment:
Reviewed deterministic design basis and severe accident scenarios of General Electric's SBWR nuclear reactor

Graduate Student Researcher
 Institute of Mathematical Modeling. Lyngby, Denmark (1994-1995)
Mathematical/Numerical Modeling:
Developed 1-D steady-state multi-group neutron diffusion mathematical model (G coupled non-linear ODEs) with void and temperature reactivity feedback and   Derived discrete equations using finite differences resulting in a block-tri-diagonal generalized eigenvalue problem and   Derived truncation errors associated with the discretization and verified the order using numerical simulations;   Developed mathematical model of the primary flow look of a nuclear reactor (BWR) for the calculation of the natural circulation flow rate and   Solved the resulting non-linear equation numerically using the Pegasus Method;   Developed mathematical flow model (one non-linear ODE coupled to two non-linear equations) for the core region of a nuclear reactor (BWR) (1-D partial equilibrium sub-cooled SP, sub-cooled TP, bulk boiling);   Developed mathematical model (one non-linear ODE) for heat flow (diffusion and convection) for water cooled cylindrical nuclear fuel pins and   Derived semi-analytical solution;   Derived truncation errors associated with the discretization and verified the order using numerical experiments
Computer simulations:
Performed design study (ran computer simulations) for a natural circulation nuclear reactor (BWR);   Calculated homogenized neutron cross-sections using the collision probability code, cccmo
C code development:
Completed one large project with more than 20,000 lines of source code for the numerical simulation of a natural circulation nuclear reactor (BWR);   Used Borland C and GNU C compiler suites under Windows;   Developed numerical sub-routines solving generalized eigenvalue problems using the power and inverse power method;   Developed numerical sub-routines for direct solution of block tri-diagonal systems of linear equations;   Implemented library of routines for solving non-linear equations (Pegasus method, fixed point iteration, secant method);   Developed MATLAB output generator for output of C data structures in .mat-file format;   Developed routines for cubic spline interpolation (data fitting)
MATLAB code development:
Developed m-scripts for solving generalized eigenvalue problems using the power and inverse power method;   Developed suite of m-scripts for simulating the natural circulation flow rate in a nuclear reactor (BWR)


Management skills: Mentoring;   Reviewed/assessed research;   Coauthored annual progress reports;   Wrote technical proposals including budgets etc;    Gave technical presentations at conferences, symposia and meetings

Languages: Fluent: Danish, English;   Comprehensive: German;   Beginnings: Spanish

Operating Systems: Linux, Windows (dos, 3.11, 95, 98, NT, 2000, XP), HPUX, Solaris

Key software experience: MATLAB, Portland Group Compiler Suite, GNU C/C++ Compiler Suite, Borland C/C++ Compiler Suite, Maple, MCNP (Monte-Carlo code), MS Office Suite, ArgoUML, Emacs, Xfig

OOP/C++: Skilled in producing highly efficient C++ code;   Familiar with the use of the C++ Standard and the UML Specification

Python code development: Developed Linux script for printing a file identification header for PostScript files

Web design: Designed and implemented my web site www.jakobchr.com

Linux system administration: Installed network print server facilities, set up local networks, recompiled Linux kernels, installed and upgraded software, hardware and drivers. Have 7+ years of experience

LaTeX and Emacs: Developed extensive macro library for scientific typesetting in LaTeX;   Developed macros for extensive text and data manipulation in Emacs

Education/ Awards

PhD, Department of Nuclear Engineering, University of California, Berkeley (2003)
MS, Electrical Engineering, Technical University of Denmark (1995)
Received various fellowships at UC Berkeley and awards from private foundations (1997-2001)


Professional Member of SIAM, Society for Industrial and Applied Mathematics
Professional Member of ACM, The Association of Computing Machinery
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