Under whose guidance did the writer of the article 'The Deep Ritz method: A deep learning-based numerical algorithm for solving variational problems' obtain his Ph.D. degree?
Björn Engquist
authored by Weinan E. E Weinan, E. W. Weinan, E. Wei<unk>nan and affiliated with Beijing Institute of Big Data Research, China. (2017) authored by Weinan E. Ling Lin et al.: A numerical method for the study of nucleation of ordered phases. (2017) authored by Weinan E. Ling Lin et al.: A Joint Learning of Response Ranking and Next Utterance Suggestion in Human-Computer Conversation System. (2017) E Weinan 2YrMeanCitedness 5.32307672500610351565, no. Stat. '<unk>., pp. Petersburg. 1. <unk>nWeinan E, and Bjorn Engquist. 5 (2002). " Physical Review B 66, no. 1 (2003): 87-132.
[INST]
Utilize the provided context information, to generate answers to the following question: 
- Generate the answer to the question based on the provided context.
- Avoid including any explanations or apologies in your responses.
- Only respond to questions that ask for the answer to the target question without any additional information.
- Strictly provide the answer without any additional text.
Question: Under whose guidance did the writer of the article 'The Deep Ritz method: A deep learning-based numerical algorithm for solving variational problems' obtain his Ph.D. degree?
Context: authored by Weinan E. E Weinan, E. W. Weinan, E. Wei<unk>nan and affiliated with Beijing Institute of Big Data Research, China. (2017) authored by Weinan E. Ling Lin et al.: A numerical method for the study of nucleation of ordered phases. (2017) authored by Weinan E. Ling Lin et al.: A Joint Learning of Response Ranking and Next Utterance Suggestion in Human-Computer Conversation System. (2017) E Weinan 2YrMeanCitedness 5.32307672500610351565, no. Stat. '<unk>., pp. Petersburg. 1. <unk>nWeinan E, and Bjorn Engquist. 5 (2002). " Physical Review B 66, no. 1 (2003): 87-132.
[/INST] Answer:
