Professor Li is a huge professor, great teacher and true scholar. His passing is a huge loss to all of us and the world of science. To me, as a student, Professor Li is always the best professor, advisor and teacher in the world. He will always be missed and his teaching is always in my heart. May Professor Li rest in peace.
Best Regards,
jason choi
18-11-2020
With utmost admiration, respect and sadness, the colleagues of Professor Li at the University of Virginia, USA, send condolences to the Li family, to Professor Li’s many distinguished students, and to Professor Li’s eminent colleagues at the Department of SEEM at CUHK. Professor Li served on the faculty of UVA, including as Associate Director of the Center for Risk Management of Engineering Systems, in 1987 to 1994.
Sincerely,
James H. Lambert,
Department of Engineering Systems & Environment, University of Virginia, USA
Professor Li Duan is our old and beloved friend for more than 30 years. We are deeply saddened by his untimely death, and hereby extend our deepest condolences to his wife, Ms. Lu Xiuying and his family!
李端教授是我们30多年的挚爱之友。 我们对他过早的去世深感悲伤，特此向他的妻子陆秀英女士及其家人致以最深切的慰问！
Professor Duan Li is our old and beloved friend for more than 30 years. We are deeply saddened by his untimely death, and hereby extend our deepest condolences to his wife, Ms. Lu Xiuying and his family!
李端教授是我们30多年的挚爱之友。 我们对他过早的去世深感悲伤，特此向他的妻子鲁秀英女士及其家人致以最深切的慰问！
Sincerely，
Joanne Z. Yu and Guodong Fang
Retired NIH Biologist (JZY) and FDA Senior Clinical Reviewer (GDF)
Rockville, MD 20855
USA
I was shocked and saddened to learn about Duan’s sudden death on Monday evening. I had already known that Li Duan was sick and I wished him the best with his treatment. I thought the worst part was over because I was informed that he had responded well to surgery and chemotherapy, and that he had returned to work.
Duan joined Chinese University in 1994 and City University in 2017. I am lucky to have been good colleagues with him in both institutions and as a close family friend. Duan was known for his rigorous scholarships, broad knowledge, and exemplary achievements in many fields. Duan’s conscience was a model of our time. Duan was a modest gentleman to his friends and colleagues, and Duan’s care to his family was unparalleled as a husband and father.
I feel lucky and proud to have been friends and colleagues with Duan.
It came so sudden and shocked to know that Professor Li Duan has left us, as we still saw his messages in our WeChat group not long ago. Professor Li is a smart, visionary, rigorous and creative scholar. It is my deepest honor to be his PhD student and this has changed my life and career. Professor Li cares about his students and continues to support us even after our graduation. Your sincere smiling face, sense of humor and serious are all beard in my mind. You are always my role model as a scholar and a human being. May Professor Li rest in peace.
I was shocked with the sad news. Professor Li is an exceptional scholar, a great friend, and an affable elder brother, with whom I always felt comfortable. Remember the time in Hong Kong and Hangzhou, forever.
With deep sympathy,
Guochuan Zhang
Zhejiang University
Professor Li Duan is my close friend and school fellow of SJTU , our pure friendship keeps more than 30 years. I am shocked and saddened very much by his sudden passing. My wife and I send the deepest condolences to his wife Ms. Lu Xiuying and his family!
Sincerely,
Zhichu FANG, PhD
Emeritus Professor of Shanghai Jiao Tong University (SJTU)
I am saddened that Prof. Li has bid farewell to us in our journey through life. He and I were still chatting last month and I was under the impression that he was recovering well. Maybe he already knew what was going to happen. He chose to keep it to himself and calmly accepted the fate ahead. He just wanted to spend his last days like every other day in life.
Prof. Li is a partner and a friend. He is someone with an open mind to new ideas and someone with a strong drive to support young people to pursue the next evolution. I am thankful for his support and encouragement along the way. It is a privilege to work with him on many meaningful initiatives.
I am grateful that Prof. Li and I have crossed our paths in life and shared a memorable time. Wherever he is now, I hope that he stays happy and strong. We will continue to live up to his pursuit as the beacon he has kindled continue to light our way ahead.
Edward Du
Prof. Duan Li and Xiao-Ling Sun’s tutorials and books on non-linear integer programming led me into the area of discrete optimization, although I did my Ph.D. at HKUST and never had the chance to meet these two great researchers in person. I knew that Prof. Xiao-Ling Sun passed away a few years ago, coincidentally also after a long fight against cancer. Prof. Duan Li was a very kind guy, who established a scholarship named after Prof. Sun, to sponsor the high school students in Prof. Sun’s hometown in Jiangxi to proceed with their post-secondary education. I can feel that both professors were not only outstanding researchers, but also kind people, dedicated to helping everyone and contributing to the society.
Deeply saddened by this loss of a dear colleague. His brilliance and kindness touched many lives. A true gentleman scholar. He is will sorely missed. Heart-felt condolences to his family.
This is really a sad news. Prof. Li Duan was a very decent person and respectable scholar…
Professor Duan Li was a great, highly respected, and humble scholar. I had the honor to learn from him in a postgraduate course and on other occasions at CUHK SEEM. He was always diligent and passionate about research. While I was not in his research group, he often offered me helpful advice on my study and career. He was a role model young researchers could learn from. May Professor Li rest in peace.
I am really shocked by this sad news of Prof. Li, a very kind professor with many outstanding contributions.
With my heartfelt condolences, may Prof. Li’s soul rest in peace.
Professor Li Duan is a great scholar, professor and leader. He is our role model. I always remember his warm smile and kind encouragement. We will miss him deeply. May Professor Li Duan rest in peace.
I was shocked and deeply saddened by this loss of a gentleman scholar. Memories of vivid and warm scenes of our meeting with him and his son in England a few years ago sprang to mind. Duan will be sorely missed with his brilliance and kindness. My heart-felt condolences goes to his family.
I had the privilege of being Prof. Li Duan’s colleague at the Chinese University of Hong Kong from 2007-2009. I have always had the utmost respect for him not only for his outstanding scholarly accomplishments and intelligence but also for his humble, calm, caring, and positive attitude. He was such a kind person and truly a great role model. I send my sincere condolences to his family. He will certainly be missed.
As a classmates in Shanghai Jiaotong University and one of my best friends，I know Li Duan and his family for forty years，His wisdom and humble are so impressive，he is a great father，loves and cares his family so much，I was shocked and saddened by his sudden death，We will miss him deeply，May him rest in peace.
I couldn’t stop my tears running out when I heard the news. You were so kind, the truly gentleman. I always remember your words. Like three years ago I wrote to you “wish you all the best no matter where you are. Thank you Professor Li”. Rest in peace.
My deepest condolences to you and your family
This is Tian Ni. I’m a student of Prof. Duan Li, a class of 2004 CUHK SEEM. I’m currently living in the Bay Area working for Facebook as a Data Scientist. I’m so heartbroken and sorry to hear Prof. Duan Li passed away from reading Prof. Janny’s post in INFORMS group email. I want to take my time to write this email to share my story here to memorize Prof. Li as a great teacher, wonderful mentor, a restless servant who cared for everybody around him.
I got admitted into CUHK for a Bachelor of Engineering in SEEM in 2004 as the 1st group of mainland students coming to Hong Kong for college from Sichuan Province. I still remember at that time there wasn’t even an admission office in Chengdu so I had to fly to Shanghai for the interview. Prof. Xiaoqiang Cai and then Chairman of SEEM Prof. Duan Li were interviewing me and my English was so shaky that I couldn’t even do a good opener to introduce myself. Prof. Li calmed me down and asked me to switch back to Chinese and told me that the interview was more about your character, your personal quality and your potential. I apparently had a miserable interview but I was trusted to get the offer which completely changed my life.
I was lucky with 15 fellow mainland students who got into CUHK SEEM in 2004. During the 4 years of college life, Prof. Duan Li led and organized mainland students dinners each year and spent time with us to understand our life, our study, if we have any difficulties that he can help and support, like a mentor, like an elder, like a father. We got the privilege as mainland students to get assigned a Professor as our mentor to take care of us. Prof. K.P. Lam was my mentor and Prof. Shuzhong Zhang instructed my final year dissertation. When I was about to graduate, I wanted to continue my graduate study oversea. I need a third person to write me a recommendation letter besides Prof. K.P. Lam and Prof. Shuzhong Zhang. Prof. Duan Li was so generous and dedicated to provide me the support at the last minute and wrote me a strong recommendation which helped me realize my dream to continue my graduate study in the United States and eventually started my career at General Motors global R&D Operations Research lab and now Facebook.
I met Prof. Duan Li and Prof. Nan Chen last year during the INFORMS annual meeting in Seattle. Prof. Li was still like his old self, smiles, energetic, kind, asking my everything about my career, about my family, about my plans. I was joking with him if he’s still wearing the long socks up to his knees to play Ping Pong with his students. That’s probably the biggest pressure that Prof. Li ever put on his students. He was laughing and asked me if that’s the only memory I had with him in SEEM. Certainly much more than that and that’s why I wanted to share it here and I believe it’s not only representing my personal experience but should represent all the mainland students and everybody who interacted with Prof. Li before.
Hope you Rest In Peace Prof. Li. Your spirit will forever inspire us!
Best Wishes,
Tian Ni
Class of 2004 CUHK SEEM
It’s very sad to hear the news as Prof. Li Duan was a very respectful colleague to all of us and had made many contributions to SEEM and CUHK.
He will be dearly missed.
The first word I heard from Professor Li was “I am a control guy.” during an interview.
周一下午，我恰与数位有意申请港校的同学谈及李端教授治学之严谨，深夜即收到噩耗，再难入眠。李端教授的逝世是学术界的巨大损失，愿老师安息。
I am saddened by the sudden passing of Prof. Li Duan. Prof. Li and I served in the various committees in the Faculty of Engineering, CUHK. His integrity, sense of fair play, and righteousness was well respected by all. This is great loss to the academic community in Hong Kong. He will be sorely missed. My sincerest condolences to his family.
It is my sincerest sympathy for this terrible loss. I will always remember Prof Li’s generous help in my works and studies in the past ten years.
In the memory of Professor Duan LI
Professor Duan Li and I met each other when he joined Department of Systems Engineering and Engineering Management, the Chinese University of Hong Kong in 1995. His office was right next to mine in Ho Sin Hang Engineering Building. I remember that Duan walked into my office on his first day of work to convey his courteous greeting. His friendly smile marked the beginning of 26 years of friendship and scholarship.
Duan is an expert in financial engineering, optimization, and systems engineering. His seminal work in non-convex optimization, multi-objective optimization, and integer optimization shaped the development of research in these fields. Particularly, his research into multi-period dynamic mean-variance portfolio optimization led into fundamental impact in return and risk analysis. Duan’s contributions to FinTech were not limited within the realm of academia. In the City University of Hong Kong where he was Associate Provost in Strategic Planning, he played a pivotal role in the formation of AI Powered Financial Technologies Limited. The mission of the company is to promote the development of Financial Technologies in Hong Kong.
Duan was very gentle to his family, friends, colleagues, and students except not so much so while he was playing table-tennis against you. His killer instinct did not let him yield a point and his soft smile hid his elusive move. Standing against him across the table made you scare of what he was going to do next. Before you changed your strategy to deal with his attack, your game was over.
Duan was a beloved husband, a kind father, an inspiring teacher, a great scholar, and a dependable friend. We are deeply saddened by his departure, but we will remember him for his friendship and scholarship.
I am not in the same department as Prof. Li Duan, also did not have a chance of working with him side by side. During 2011-2014, I got to see him (then the Chairman of SEEM Department) on regular basis in the faculty’s executive committee meetings. He did not speak a lot in meetings. Every time he spoke out, I heard deep thoughts and principles. There was one time that he came to say to me “you have done a good job” after a long meeting in which I had some debate with other colleagues. I was so touched and I know he really meant that.
Our former Dean Prof. CP Wong kept confusing Li Duan and Li Dan (my name). It was my honour.
Miss you Li Duan.
Professor LI Duan was so kind, and was a wonderful colleague at CUHK! He will be deeply missed. My sincerest condolences to his family.
I just heard the news today and am still in shock. When I first went to UVA Systems Engineering as a graduate student in 1990, I started to get to know him and his family. I looked up to him as a mentor and a good friend. He was a wise scholar and a kind person. He was witness to the me falling in love and getting married with my wife and was our honorable guest in the wedding. I last talked to Professor Li last October letting him know of my wife’s unfortunate passing due to an accident. I am so sad to hear that he’s passed, too but comforted somehow knowing that he has good company in Heaven. Rest in Peace.
Dr. Li Duan was a high level Pingpong player. We used to play Pingpong together in Charlottesville. VA. He will be truly missed!
Please send my condolence to Dr. Li’s family
Professor Li is a huge professor, great teacher and true scholar. His passing is a huge loss to all of us and the world of science. To me, as a student, Professor Li is always the best professor, advisor and teacher in the world. He will always be missed and his teaching is always in my heart. May Professor Li rest in peace.
Best Regards,
jason choi
18-11-2020
With utmost admiration, respect and sadness, the colleagues of Professor Li at the University of Virginia, USA, send condolences to the Li family, to Professor Li’s many distinguished students, and to Professor Li’s eminent colleagues at the Department of SEEM at CUHK. Professor Li served on the faculty of UVA, including as Associate Director of the Center for Risk Management of Engineering Systems, in 1987 to 1994.
Sincerely,
James H. Lambert,
Department of Engineering Systems & Environment, University of Virginia, USA
李端教授是动态多周期mean-variance领域的开拓者引领者。特别，他带领我们长达11年的不懈努力彻底解决Harry Markowitz教授所关心的mean-variance带卖空约束解在多周期框架下的猜想。50多天前我们还在海边讨论这一领域的最新进展，10天前还在听他的学术报告…… 李端教授是我永远的榜样，深深地怀念他。
Professor Li Duan is our old and beloved friend for more than 30 years. We are deeply saddened by his untimely death, and hereby extend our deepest condolences to his wife, Ms. Lu Xiuying and his family!
李端教授是我们30多年的挚爱之友。 我们对他过早的去世深感悲伤，特此向他的妻子陆秀英女士及其家人致以最深切的慰问！
Professor Duan Li is our old and beloved friend for more than 30 years. We are deeply saddened by his untimely death, and hereby extend our deepest condolences to his wife, Ms. Lu Xiuying and his family!
李端教授是我们30多年的挚爱之友。 我们对他过早的去世深感悲伤，特此向他的妻子鲁秀英女士及其家人致以最深切的慰问！
Sincerely，
Joanne Z. Yu and Guodong Fang
Retired NIH Biologist (JZY) and FDA Senior Clinical Reviewer (GDF)
Rockville, MD 20855
USA
I was shocked and saddened to learn about Duan’s sudden death on Monday evening. I had already known that Li Duan was sick and I wished him the best with his treatment. I thought the worst part was over because I was informed that he had responded well to surgery and chemotherapy, and that he had returned to work.
Duan joined Chinese University in 1994 and City University in 2017. I am lucky to have been good colleagues with him in both institutions and as a close family friend. Duan was known for his rigorous scholarships, broad knowledge, and exemplary achievements in many fields. Duan’s conscience was a model of our time. Duan was a modest gentleman to his friends and colleagues, and Duan’s care to his family was unparalleled as a husband and father.
I feel lucky and proud to have been friends and colleagues with Duan.
It came so sudden and shocked to know that Professor Li Duan has left us, as we still saw his messages in our WeChat group not long ago. Professor Li is a smart, visionary, rigorous and creative scholar. It is my deepest honor to be his PhD student and this has changed my life and career. Professor Li cares about his students and continues to support us even after our graduation. Your sincere smiling face, sense of humor and serious are all beard in my mind. You are always my role model as a scholar and a human being. May Professor Li rest in peace.
Sincerely,
Mei Choi CHIU
能成为李老师的学生是非常非常幸运的事情
以至于失去李老师，长久只觉得千言万语难以成言。李老师对自己要求极高，却总是对我们很宽容，很体谅，淳淳教诲，诲人不倦。直至如今，我写下这句话时还能清晰地想到在很多个过往瞬间同时存在的李老师的笑容，包容的笑容、鼓励的笑容，重叠在一起。耳边还会有李老师的笑声和鼓励的话语，还有准确而又incentive的意见建议。
李老师是我的导师，不仅是学业上的导师，教我们严谨治学、热爱科研，令人高山仰止；更是生活上的导师，教我热爱生活、与人为善、平衡工作和生活。李老师的最后一段时间更是以身作则地让我懂得乐观坚强、为人着想、富有责任心。
李老师首先是个醇厚长者，包容而远视，谦逊而富有社会责任感；但又同时偶尔会像个孩子，纯粹而专注，热情又乐观，感染着身边的所有人
希望天堂没有病痛，希望李老师永远开心。永远怀念
I was shocked with the sad news. Professor Li is an exceptional scholar, a great friend, and an affable elder brother, with whom I always felt comfortable. Remember the time in Hong Kong and Hangzhou, forever.
With deep sympathy,
Guochuan Zhang
Zhejiang University
太突然了，端叔真的是好教授，学术造诣高，为人和蔼负责。
哀悼、缅怀R.I.P
李端教授是我极为敬重的好老师。为人谦逊和蔼，学术造诣非常高。在我最困难的时候，给予我很大的鼓励和支持。当时的鼓励，学生一直铭记在心。李老师的逝去，对我们是非常大的打击。
愿李老师安息。学生永远怀念。
姜力
It was a shocking and saddening news. It has been a privilege and honour to have spent some time with Prof. Li at CityU.
周一收到group的信息，得知李老师弥留，傍晚已离世，实在让人难以接受。这两天每每想起李老师，悲伤止不住涌上心头。在学术和工作上，李老师总是兢兢业业、严于律己、宽以待人。非常感恩李老师，在人生漫漫旅途上，有幸得到这么好的导师，实乃我们后辈的福气。仰之弥高，钻之弥坚，老师音容宛在，多么想还有机会再聆听老师的教导。愿老师安息，学生永远怀念您。
Professor Li Duan is my close friend and school fellow of SJTU , our pure friendship keeps more than 30 years. I am shocked and saddened very much by his sudden passing. My wife and I send the deepest condolences to his wife Ms. Lu Xiuying and his family!
Sincerely,
Zhichu FANG, PhD
Emeritus Professor of Shanghai Jiao Tong University (SJTU)
I am saddened that Prof. Li has bid farewell to us in our journey through life. He and I were still chatting last month and I was under the impression that he was recovering well. Maybe he already knew what was going to happen. He chose to keep it to himself and calmly accepted the fate ahead. He just wanted to spend his last days like every other day in life.
Prof. Li is a partner and a friend. He is someone with an open mind to new ideas and someone with a strong drive to support young people to pursue the next evolution. I am thankful for his support and encouragement along the way. It is a privilege to work with him on many meaningful initiatives.
I am grateful that Prof. Li and I have crossed our paths in life and shared a memorable time. Wherever he is now, I hope that he stays happy and strong. We will continue to live up to his pursuit as the beacon he has kindled continue to light our way ahead.
Edward Du
Prof. Duan Li and Xiao-Ling Sun’s tutorials and books on non-linear integer programming led me into the area of discrete optimization, although I did my Ph.D. at HKUST and never had the chance to meet these two great researchers in person. I knew that Prof. Xiao-Ling Sun passed away a few years ago, coincidentally also after a long fight against cancer. Prof. Duan Li was a very kind guy, who established a scholarship named after Prof. Sun, to sponsor the high school students in Prof. Sun’s hometown in Jiangxi to proceed with their post-secondary education. I can feel that both professors were not only outstanding researchers, but also kind people, dedicated to helping everyone and contributing to the society.
Deeply saddened by this loss of a dear colleague. His brilliance and kindness touched many lives. A true gentleman scholar. He is will sorely missed. Heart-felt condolences to his family.
This is really a sad news. Prof. Li Duan was a very decent person and respectable scholar…
Professor Duan Li was a great, highly respected, and humble scholar. I had the honor to learn from him in a postgraduate course and on other occasions at CUHK SEEM. He was always diligent and passionate about research. While I was not in his research group, he often offered me helpful advice on my study and career. He was a role model young researchers could learn from. May Professor Li rest in peace.
I am really shocked by this sad news of Prof. Li, a very kind professor with many outstanding contributions.
With my heartfelt condolences, may Prof. Li’s soul rest in peace.
Professor Li Duan is a great scholar, professor and leader. He is our role model. I always remember his warm smile and kind encouragement. We will miss him deeply. May Professor Li Duan rest in peace.
I was shocked and deeply saddened by this loss of a gentleman scholar. Memories of vivid and warm scenes of our meeting with him and his son in England a few years ago sprang to mind. Duan will be sorely missed with his brilliance and kindness. My heart-felt condolences goes to his family.
I had the privilege of being Prof. Li Duan’s colleague at the Chinese University of Hong Kong from 2007-2009. I have always had the utmost respect for him not only for his outstanding scholarly accomplishments and intelligence but also for his humble, calm, caring, and positive attitude. He was such a kind person and truly a great role model. I send my sincere condolences to his family. He will certainly be missed.
As a classmates in Shanghai Jiaotong University and one of my best friends，I know Li Duan and his family for forty years，His wisdom and humble are so impressive，he is a great father，loves and cares his family so much，I was shocked and saddened by his sudden death，We will miss him deeply，May him rest in peace.
I couldn’t stop my tears running out when I heard the news. You were so kind, the truly gentleman. I always remember your words. Like three years ago I wrote to you “wish you all the best no matter where you are. Thank you Professor Li”. Rest in peace.
My deepest condolences to you and your family
This is Tian Ni. I’m a student of Prof. Duan Li, a class of 2004 CUHK SEEM. I’m currently living in the Bay Area working for Facebook as a Data Scientist. I’m so heartbroken and sorry to hear Prof. Duan Li passed away from reading Prof. Janny’s post in INFORMS group email. I want to take my time to write this email to share my story here to memorize Prof. Li as a great teacher, wonderful mentor, a restless servant who cared for everybody around him.
I got admitted into CUHK for a Bachelor of Engineering in SEEM in 2004 as the 1st group of mainland students coming to Hong Kong for college from Sichuan Province. I still remember at that time there wasn’t even an admission office in Chengdu so I had to fly to Shanghai for the interview. Prof. Xiaoqiang Cai and then Chairman of SEEM Prof. Duan Li were interviewing me and my English was so shaky that I couldn’t even do a good opener to introduce myself. Prof. Li calmed me down and asked me to switch back to Chinese and told me that the interview was more about your character, your personal quality and your potential. I apparently had a miserable interview but I was trusted to get the offer which completely changed my life.
I was lucky with 15 fellow mainland students who got into CUHK SEEM in 2004. During the 4 years of college life, Prof. Duan Li led and organized mainland students dinners each year and spent time with us to understand our life, our study, if we have any difficulties that he can help and support, like a mentor, like an elder, like a father. We got the privilege as mainland students to get assigned a Professor as our mentor to take care of us. Prof. K.P. Lam was my mentor and Prof. Shuzhong Zhang instructed my final year dissertation. When I was about to graduate, I wanted to continue my graduate study oversea. I need a third person to write me a recommendation letter besides Prof. K.P. Lam and Prof. Shuzhong Zhang. Prof. Duan Li was so generous and dedicated to provide me the support at the last minute and wrote me a strong recommendation which helped me realize my dream to continue my graduate study in the United States and eventually started my career at General Motors global R&D Operations Research lab and now Facebook.
I met Prof. Duan Li and Prof. Nan Chen last year during the INFORMS annual meeting in Seattle. Prof. Li was still like his old self, smiles, energetic, kind, asking my everything about my career, about my family, about my plans. I was joking with him if he’s still wearing the long socks up to his knees to play Ping Pong with his students. That’s probably the biggest pressure that Prof. Li ever put on his students. He was laughing and asked me if that’s the only memory I had with him in SEEM. Certainly much more than that and that’s why I wanted to share it here and I believe it’s not only representing my personal experience but should represent all the mainland students and everybody who interacted with Prof. Li before.
Hope you Rest In Peace Prof. Li. Your spirit will forever inspire us!
Best Wishes,
Tian Ni
Class of 2004 CUHK SEEM
It’s very sad to hear the news as Prof. Li Duan was a very respectful colleague to all of us and had made many contributions to SEEM and CUHK.
He will be dearly missed.
My Condolences To his family.
回忆李端教授生前二三事
惊悉李端教授于2020年11月16日不幸逝世，不胜哀悼。沉痛之余回忆起我所知道的李端教授生前二三事。
我第一次见到李端教授是在1990年元旦过后，我从美国俄亥俄州莱特州立大学转学到得克萨斯州立大学，途中经过维吉尼亚夏洛特维尔市就去看望李端一家，顺便想参观著名的弗吉尼亚大学。那时李端在该校系统工程系任副教授。我搭乘的灰狗巴士因晚点到达夏市已是半夜。车外寒风凛冽，刚下车就看到李端教授风度翩翩站在候车厅向我招手, 心里一阵温暖。我们上车后聊了些白天的大风雪，李端教授注视着冰雪茫茫的山路, 非常专注的开车。突然车在一个下坡路上打滑，转了360度后冲向路边的悬涯，一瞬间却又稳稳得停在了路边，人车丝毫无损。继续开车到家后，李瑞教授第一时间同他太太讲了路上险情，解释了他当时怎样及时稳妥的刹车。我那时还不会开车，听说后才意识到问题的严重性，心中不禁暗自庆幸和佩服李端教授的高超车技。第二天李端教授在很忙的工作中，抽空陪我参观了弗吉尼亚大学的工程学院并会见了研究生学生顾问，最后又送我到灰狗车站，开启了我的近三十年在得克萨斯州的学习和生活之路。
李端教授太太家和我太太家是世代好友，老一辈的友谊也传承到了下一代。我到美国求学得到了李端教授的很大帮助，记得1989年秋天刚到莱特大学时，研究生院已开学，我在银行的学费还没到帐，心里有些着急。李端教授得知后，立刻同他的朋友当时的莱特大学中国学生会主席联系，由他朋友先用信用卡把我的学费给垫付了。李端教授为人正直乐于助人，他朋友圈之广人缘之好可略见一斑。
2015年春天李端教授来得克萨斯州开会，我开车从达拉斯到奥斯汀，接他和他大儿子到我家住了一天。时间虽短交谈甚欢，我亲身感受到了李瑞教授知识渊博，学术精湛，逻辑严谨，思维敏捷。他对当代科学的追求，对科学技术在金融领域的应用，对中国未来的发展都有独到的见解，充满着期待。在回奥斯汀的路上，我约他下次再来得州多住几天，我俩都是乒乓运动的爱好者，可以练练球打一场比赛，李端教授很高兴得答应了。现在李端教授走了，每每想到这一约定再也不能实现，心里充满无限伤感。李端教授对科学和真理孜孜不倦的追求，对生活和工作奋力拼搏的精神，对朋友和他人真诚热情的关爱是一份永恒的财富，将永远留在我们大家的心中。
谨以此文表达我，我太太朱季华和我们儿子汤东波对李端教授的深切悼念。
汤银炜
2020年11月23日于美国达拉斯
The first word I heard from Professor Li was “I am a control guy.” during an interview.
周一下午，我恰与数位有意申请港校的同学谈及李端教授治学之严谨，深夜即收到噩耗，再难入眠。李端教授的逝世是学术界的巨大损失，愿老师安息。
I am saddened by the sudden passing of Prof. Li Duan. Prof. Li and I served in the various committees in the Faculty of Engineering, CUHK. His integrity, sense of fair play, and righteousness was well respected by all. This is great loss to the academic community in Hong Kong. He will be sorely missed. My sincerest condolences to his family.
Rest in peace Prof. Li. You will be missed…
一周前我在惠州听到您去世的消息，近在咫尺，竟然无法到香港去探望，去年12月29日在山东莒南的见面竟然成了永别，还说好2020年去香港访问（未能成行）。
1997年5月13日我成为您的学生，二十三年来在您的引领下，读书、做研究、写论文、带学生、对待家人，学着您为人处世，学着您如何和气地说话，如何专心地倾听，如何开心地笑，如何有界限感。
由于疫情，目前去不了香港，能做的并不多，但是我会谨记教诲，学您做事，学您做人，学您对待生命。
感谢香港，因为香港中文大学；感谢香港中文大学，因为SEEM；感谢SEEM，因为您！
王军
青岛大学
2020年11月23日
Wang Jun, please send me an email when you see this. Thanks.
《临江仙》哭李端
晴空霹雳九州炸，
凄雨狂风邪刮。
冠英殒落坠天涯。
科学失巨子，
悲掩万千家。
三十余年如流水，
浩淼温润清佳。
只手折桂世人夸。
春风和汗水，
苗发遍中华。
It is very sad to know this.
Prof Li, thank you very much for your help in the past few years. You will be missed. May you rest in peace.
作为李老师最后的一批学生之一，我仅分享一些故事，表达对老师的崇敬与怀念。
：刚接到老师离世的噩耗时，我与大部分组里的同学一样表示不敢相信，因为老师两周前才精力十足给大家开完组会，微信朋友圈还在探讨着美国大选花落谁家，即使离世三日前师兄说老师住院需要暂时修养，我也从未料想过这一天的来临。从养和医院回到家，我脑海中再次浮现最后老师憔悴而又单薄的身躯、熬红的眼眶、微微张开的双唇，不禁抽泣，因为这样的对比实在是太强烈。癌症病人的痛苦，并不是一般人能够体会和理解的，但是李老师能够让身边的八个博士在走前没有丝毫察觉，我觉得并不是一般的信念和用心就能做到的。这是一种浸润到每个毛孔、每条血管的乐观、善良、涵养驱使下的本能行为，老师把欢乐留给自己的学生，把疾病、痛苦、压力嚼碎自己咽下。他说过香港的有轨电车25年第一次坐，但没有说这趟列车通往医院；他说过太太买的鲍鱼很划算，却没有说自己是临走之前赶快尝尝；他还说过赶紧选题帮看看，却没说自己已经快要没有时间了！！！开学初老师突然问我在不在学校，刚好看能不能见面（非常羡慕当时见到的同学），我正在家就问下午可否，老师发来【开心】的表情说下次吧！但是下次是何次，相逢是何年…您已经踏上去天国的列车，我还在烟火人间…我们还能否再次视频联线，听听您说天国的奇闻逸事？现如今我渐渐接受您离去的事实，每每在现实中碰到困难，才发现纵使运筹千里都是您留下的后路，co-supervisor您早已选好，资金早已部署，要读的书目文献都留好，您过去的两个月难道不是日日殚精竭虑在为我们未来的四年筹谋计划吗？对一个人如此尚且不易，更何况对很多人都是如此，听闻此事，学生全家均为之感慨、落泪！细雨闲敲芳菲李，春风笑看青云端。每当您拂过我们身旁，我们便知道未来的路途并不孤独！
It is my sincerest sympathy for this terrible loss. I will always remember Prof Li’s generous help in my works and studies in the past ten years.
In the memory of Professor Duan LI
Professor Duan Li and I met each other when he joined Department of Systems Engineering and Engineering Management, the Chinese University of Hong Kong in 1995. His office was right next to mine in Ho Sin Hang Engineering Building. I remember that Duan walked into my office on his first day of work to convey his courteous greeting. His friendly smile marked the beginning of 26 years of friendship and scholarship.
Duan is an expert in financial engineering, optimization, and systems engineering. His seminal work in non-convex optimization, multi-objective optimization, and integer optimization shaped the development of research in these fields. Particularly, his research into multi-period dynamic mean-variance portfolio optimization led into fundamental impact in return and risk analysis. Duan’s contributions to FinTech were not limited within the realm of academia. In the City University of Hong Kong where he was Associate Provost in Strategic Planning, he played a pivotal role in the formation of AI Powered Financial Technologies Limited. The mission of the company is to promote the development of Financial Technologies in Hong Kong.
Duan was very gentle to his family, friends, colleagues, and students except not so much so while he was playing table-tennis against you. His killer instinct did not let him yield a point and his soft smile hid his elusive move. Standing against him across the table made you scare of what he was going to do next. Before you changed your strategy to deal with his attack, your game was over.
Duan was a beloved husband, a kind father, an inspiring teacher, a great scholar, and a dependable friend. We are deeply saddened by his departure, but we will remember him for his friendship and scholarship.
C.H. Cheng
November 25, 2020
听到我们亲爱的朋友李端的噩耗，我和我的妻子都感到震惊和悲痛。李端是我们那一代留学生中的佼佼者，是我们留美学子的楷模，是很多UVA学生学者的良师益友。我是在弗吉尼亚大学读博期间认识李端的，他那时已是系统工程系的副教授，但他毫无架子，十分平易近人。他太太鲁秀英也是非常的贤慧，我们两家常有往来。我毕业那年，因为经济不景气工作不好找，李端夫妇得知我找到了工作，非常为我高兴，摆了一桌子菜为我们饯行，那晚的欢乐情景至今历历在目。后来李端去了香港中文大学，我们虽互通过几次信，但还是逐渐失去了联系。几年前有一次我去参加运筹和管理学年会(INFORMS)，在与会者名单中看到李端的名字，心想这下可以续上联系了，但可惜那次李端并未成行，虽觉遗憾，但认定下次一定有机会。不曾想，这次却天人永隔，再无缘相见了，不胜悲哀！祝李端一路走好，在九泉之下安息吧！亦望李端家人节哀顺便，保重身体，上苍定会佑护你们积善之家的！
回忆李端教授
早上醒来，忽然地，莫名中，想起了李端教授。时光恍惚，许多年未联系，不清楚具体情况，便随手拿起手机搜索了一下。乍看到一条不祥消息时，认为是重名。点开后看内容，才确认了他于11月16日不幸离世的信息。看到这个突然消息，无心理防备，顿感心里堵的慌。
认识李教授，是上世纪末在上海交通大学听他的一次学术讲座，关于多阶段金融投资最优化模型的创新性研究。以当时国内学术领域的研究状况，李教授的研究既超前又深入，学术价值极高。博士后研究期间，有机会赴香港中文大学访问李教授，时间虽短，收获很大。教授治学严谨、工作勤奋，学术造诣深厚，令人印象深刻。后来，因没继续跟李教授追求学术，联络渐少。
印象里，李教授身体健康，精力充沛，激情满满，活力十足。其优秀的乒乓球技艺，乐观积极的生活追求，诸多健康生活品格，很难和病患联系上。
人格魅力——是对教授的另一深刻记忆。尽管其有关最优化领域的丰硕研究成果，国际领先，享誉盛名，却始终给予周围人群谦虚、宽厚、慈祥、善良的感受。繁重的教学研究工作，对各地频繁来访学者的关照，对家庭的关爱和责任，正直大气，令人敬慕！他的突然辞世，无论对学术界还是他的家庭、同事、朋友、学生，皆属巨大损失和悲伤。
其实，早些日子就计划着有机会去香港拜访教授。上半年疫情期间，举国停摆，居家办公，有大把闲暇时间宅在家里。整理物品时，发现了很久前跟李教授访问学习时的资料、文稿，重新翻看、回忆、思考，重启对当时所讨论问题的兴趣和看法。计划着想法成熟些后，和李教授联系、讨论，不料却成人生遗憾。
教授，还记得我吗——
难忘记，世纪末的圣诞，
和您及家人共进晚餐，
听着当红歌星的演唱，
度过圣诞夜；
难忘记，世纪末的元旦，
和您及家人远足香港名山，
畅游抗日遗迹，
老榕树下许愿，
度过愉快新年。
而今日，英才早逝，
唯对天叹息:
李教授，还记得我吗？
（2020年11月26日，于上海）
尽管已过了半月有余，还是不愿相信李老师就这么走了，走的匆匆忙忙！每当想起李老师，他那亲切轻松的音容笑貌就活生生的浮现在眼前！还以为他会永远年轻！更难忘我们一起在悉尼渡过的美好时光和听他讲第一次尝试吃袋鼠肉的感受。愿他在匆忙的一生之后静静地安息吧！
尊敬的香港中文大学系统工程与工程管理系，
半个月前听说李教授不幸离世的消息，我非常的震惊并且痛心。虽然与李教授仅有邮件以及微信的简单交流，但是我深深地感受到了李教授和蔼、善良、谦逊、循循善诱的伟大品质。短短的一次微信语音交流已经足矣让我为他的人格魅力折服，他当初为我做出的指点与规划使我受益匪浅。
我是因为李教授所创办的金融科技实验室公司才有幸能够与李教授结识，在沟通过我的学历以及专业背景后，李教授收下了我的简历，并答应为我在他的公司申请研究员的职位，对我来说这是莫大的荣幸，但不知当时，李教授就已经承受着病痛的折磨。
如果您收到这封信，烦请向李教授的家人转达我的哀思。若您有李教授所创办的公司相关负责人的联系方式，也请告知我，希望我能够为李教授未竟的事业尽一份力，感谢！
沉痛悼念李端教授
王浩辰
刚知道有这个网站。写上几句以示我对李端的垂念。
听到李端驾鹤西去，深感震惊和悲痛。这消息太突然了。我都不敢相信, 也不愿意相信。
这么有才华的人,老天爷不把他留在人间,太不公平了,让人觉得天妒英才。
李端是我大学时最好的朋友和同学。我们俩志同道合，情趣相投,无話不说。
记得那时我们常常相约去复旦第一教学楼讨论一些学习难题，李端天资聪颖，
勤奋好学，思路敏捷很多难题到他手里都会迎刃而解。
我们也常常在落日的余晖中漫步在复旦的校园里,享受着晚自习前清静的时刻。
李端是打乒乓球的高手，课余时我们常在一起打球。即使到了美国，
他仍然在弗吉尼亚的家中购置了一张乒乓球台，以享受打球时的乐趣。
毕业后我们也常联系，他和鲁秀英结婚时邀请了我和我太太参加婚宴。
1982年李端考取了教育部留学奖学金，1983年赴美国攻读博士，
师从国际系统工程权威Yacov教授。我特地到他家为他送行。
1992年他开会途经旧金山,打电话给我想見見面。我说好啊,我叫他到我家吃晚饭。
他说不行,明天一早的飞机回弗吉尼亚。如果到我家(我家在硅谷的Cupertino,
开车至他旅馆单程约50分钟)吃晚饭,我得先去旧金山机场他住的酒店接他,吃完晚饭,
我得送他回他住的酒店, 我再回家,他说这样来回二次, 我会太累,
他建议我去旧金山机场他住的酒店見面,我也只能接收了,结果那天我们聊到凌晨二点半。
1996年聖诞节，李端及全家发了一封贺信给我。介绍了他们这二年在香港的生活，
三个儿子的学习情况，并说鲁秀英的广东话已达鱼目混珠的地步。
而他自己在整数规化领域里取得了一系列令人陶醉的结果。
另外一些权威评论他在凸化方面的工作是以一个开拓性的方法解决了三十年的难题。
全信热情扬谥，一个成功自豪的父亲，一个解决了难题的学者的喜悦跃然纸上。
2019年2月份我告诉他,我十月份回上海,他马上说他一定会从香港赶到上海和我碰面。
真想不到这竟然是我们之间的永别。
李端一生工作勤奋，治学严谨，知识渊博，学富五车。他在优化与控制，金融工程，
管理科学等领域取得杰出的成就。尤其是他提出的动态均值方差问题嵌入法更是
开劈了在动态收益，风险分析领域的先河。
现在我们虽然天人永隔, 但李端的音容笑貌，依然历历在目。
男儿有泪不轻弹，只是未到伤心处。现在每每回想起和李端一起的往事,
眼眶中会不由自主地泛出泪花。真的到伤心处了。
我会永远把我们之间的友情放在我记忆中最深处最美好的位置。
愿李端在天之灵安息！
I am not in the same department as Prof. Li Duan, also did not have a chance of working with him side by side. During 2011-2014, I got to see him (then the Chairman of SEEM Department) on regular basis in the faculty’s executive committee meetings. He did not speak a lot in meetings. Every time he spoke out, I heard deep thoughts and principles. There was one time that he came to say to me “you have done a good job” after a long meeting in which I had some debate with other colleagues. I was so touched and I know he really meant that.
Our former Dean Prof. CP Wong kept confusing Li Duan and Li Dan (my name). It was my honour.
Miss you Li Duan.
怀念李端教授
邻居小杜
2020年12月16日
11月15日那天晚餐时，孩子们忽然问起不知从哪里听来的“纳什均衡”，我脱口答道：“以后你们可以请教李教授，他可是这方面的专家！” 李教授还不知道，他成了我应对三个孩子问各种疑难问题的法宝。几个月前，当我告诉他们李教授上中学时自己用元器件组装电视看球赛，孩子们就认定李教授是真人版的超人Superman！说完这话，我心里不觉隐隐一沉，怎么好几天没看到李教授发朋友圈儿了？一想到前几天他还发照片为小儿子庆祝生日，我又放心了一点。
可万万没想到仅仅过了几天，鲁阿姨就发来令我震惊痛心的消息！我拿着手机在家里直转圈，完全不敢相信，赶紧去翻李教授的朋友圈。果真自11月9日后，连续十天每天都没有再更新！李教授是微信上特别积极活跃的朋友，几乎每天都会转发文章，涉及时事政治、天文地理、以及历史人文，并附上自己的几句点评。他也常常分享自己工作和生活的照片，时不时还会贴几张他家对面的吐露港晚霞。平时一打开朋友圈，李教授的头像右上方常有一个红点，提示他又有新的分享。现在，那个小红点消失了，无影无踪，再也不会跳出来给我们分享各种文章了。想到这里，我觉得心好痛！
我是通过鲁阿姨认识李教授的。那时我们是同一屋苑同一座楼的邻居，鲁阿姨知道我也有三个儿子，常和我拉家常，交流教育孩子的心得。我家孩子们最喜欢去鲁鲁奶奶家里玩，因为奶奶家是他们的“大白兔奶糖秘密基地”。鲁阿姨爱和孩子聊天，常把三兄弟逗得嘎嘎笑。李教授话不多，通常打个招呼，他就回里屋去了。三个孩子一有好吃的，就忘乎所以，笑声一浪高过一浪，我止都止不住。一会儿李教授就走出来了，我好担心三兄弟太吵，影响他工作。他向鲁阿姨挥挥手，夹着上海话问，家里不是还有那种什么什么零食吗，孩子们可以吃那个。阿姨一拍手，“对哟，怎么把这个忘记了”，赶紧去厨房翻出一袋儿好吃的出来。过一会儿，李教授好像又想起了什么，走出来冲阿姨喊，快把那什么什么零食拿出来，那个好吃，快给孩子们吃！李教授和阿姨进进出出好几趟，忙活着拿各种好吃的。每次孩子们都赖在奶奶家不肯走，事先说好的玩儿半小时，常常拖到两个多小时，走的时候每个孩子的兜里都揣满了糖果。
有一次鲁阿姨清理家里的旧书，叫我去她家一趟，看看哪些书可以留给我家三兄弟看。我兴冲冲去了，一进家门，就看见地板上堆着一摞摞书。鲁阿姨说，这些书都是她家三个孩子看过的，本想处理掉，李教授提醒她可以送给我。我连声道谢，也不客气，坐在餐桌旁的椅子上，就开始一本一本地翻。我告诉阿姨好多书都用得着，真是太好啦! 我看得正起劲儿呢，李教授从里间走出来要出门。我有些不好意思，刚才光顾着看书拣书，顺手把书摊得到处都是，把门口堵上了。李教授跨过地板上的书本，很温和地说：“你慢慢挑，我去上班了。” 李教授和阿姨送给我们很多书，我用小拖车运了好几次才搬完。那本已绝版的大开本彩色韦氏字典，现在是我们全家学习英语的绝佳工具书。今年夏天，我和大儿子看得入迷的《Kite Runner》，也是在阿姨家淘的。
大概两年前，李教授转去香港城市大学工作。听鲁阿姨说，他去城大后工作非常繁忙，常到各地出差。李教授不放心阿姨独自在家，就让阿姨留一把钥匙放在我家。鲁阿姨在家忙里忙外，有几次出门时，真的忘了带上钥匙。李教授好细心，因为他想得周到，阿姨有了备用钥匙就不用担心被锁在门外了。后来我搬到紧邻的另一个屋苑，那把钥匙也还一直放在我这里。有一回我和鲁阿姨聊天，她说收拾家时发现了一封李教授很久以前写给她的信。阿姨展开已经泛黄的信纸，读了几段给我听。她伸直胳膊把信拿得远远的，一字一句念着那些年月已久但依然热忱的文字，让我在一旁听着也感觉很幸福。
记得前年四月份，李教授在朋友圈儿发了个帖子，提到一款叫“懂鸟”的小程序，可以通过上传照片识别和查询所拍鸟类的信息。他还亲自实验，拍了一张停在中大池塘的白头翁，结果这个小程序识别成功。不久，我刚好在路上见到一只尾巴特别长的鸟，不是那些我常见的品种，所以好想探个究竟。我想起李教授的介绍，也尝试下载“懂鸟”，但折腾了一晚上，我的手机怎么都装不了。我太想知道这只鸟叫啥名儿了，犹豫了一会儿，就在晚上八点把照片发给李教授，请他有空的时候帮我查一查。发完短信我就立刻后悔了，为自己的冒昧感到内疚，这样多打扰李教授的休息啊。正坐立不安，一看手机，李教授已秒回我“懂鸟”的识别结果，那只长着长尾巴的小鸟，学名叫“鹊鸲”。
我有时也发朋友圈儿，但远没有李教授发得那么勤，多半是和孩子们一起去行山的照片。李教授常常给我的帖子点赞，或者留个言，说他收藏了几张我拍的风景。去年初春的一天，李教授发了一条朋友圈儿，说他当天独自一人去登马鞍山，两个半小时就上下来回，兴致颇高。我立刻给他留言，说我们当天也去登马鞍山了，好可惜没碰上！没想到李教授回复说：“我开车回来时，在体育场那里看到你们一家五口过马路，你先生最后赶上”，还附了一个呲牙大笑的表情。李教授生病后，我每次去行山都会把拍到的风景放在朋友圈儿，希望他能看到山野的阳光、白云、芒草和飘在空中的滑翔伞。每次看到他点赞，我都非常非常开心！
除了在网上和李教授交流，以及那次不约而同的行山，平时我见他最多是在散步的路上。我们小区旁边有一片空地，本来是一个停车场，后来政府改建为公园。这个公园一修就是两三年，我们经常在公园工地外的小路上遇到李教授。我印象中，李教授散步时常穿一件深卡其色的外套，步子不急不徐，总是若有所思的样子。有时迎头遇上了，他会问：“你们散步啊！哟，老大怎么没来？” 有一次，我们在海边散完步往回走，转过公园工地的拐角，发现李教授走在前面。孩子们立刻冲上前去，围住他打招呼。其中叫宝宝的孩子问：“李教授，您是从唐朝来的吗？” 这个无厘头的问题让李教授“哦”了一声。宝宝解释说，他有一天翻《唐诗三百首》，有了一个重大发现，书上有位诗人的名字和李教授一模一样！李教授听了宝宝的傻话乐得哈哈大笑。
现在公园快修好了，工地上的围栏和铁丝网也拆除了，里面有大片草地和各种健身设施。我和孩子们多想再看到李教授走在不远处默默思考的身影，想再和他一起散步聊天、在公园的转角处又一次偶遇！写这篇小文时，我努力回忆，发现其实我和李教授碰面交流的机会并不多。有一天清晨我们在电梯里碰到，好像当时李教授要去哪儿出差。我记得很清楚，出电梯时他对我说：“你的三个儿子都挺乖的，你要好好培养！” 李教授，您的话我一直记在心里呢！我记得您淡淡的微笑、温和的上海口音，以及您给我的帮助和鼓励。您安息吧，谢谢您！?
Professor LI Duan was so kind, and was a wonderful colleague at CUHK! He will be deeply missed. My sincerest condolences to his family.
I just heard the news today and am still in shock. When I first went to UVA Systems Engineering as a graduate student in 1990, I started to get to know him and his family. I looked up to him as a mentor and a good friend. He was a wise scholar and a kind person. He was witness to the me falling in love and getting married with my wife and was our honorable guest in the wedding. I last talked to Professor Li last October letting him know of my wife’s unfortunate passing due to an accident. I am so sad to hear that he’s passed, too but comforted somehow knowing that he has good company in Heaven. Rest in Peace.
Dr. Li Duan was a high level Pingpong player. We used to play Pingpong together in Charlottesville. VA. He will be truly missed!
Please send my condolence to Dr. Li’s family