Core Viewpoint - The article highlights the deep connection between the Yan family and the Great Wall of China, showcasing their extensive exploration and research over 40 years, culminating in the publication of a book titled "Great Wall Morphology Atlas" that aims to document and understand the architectural beauty and historical significance of the Great Wall [4][6]. Group 1: Exploration Journey - The Yan family, consisting of Yan Xinqiang and his son Yan Gongming, has visited the Great Wall over a thousand times since 1984, traveling from Beijing to various provinces including Hebei, Shanxi, and even Ningxia and Gansu [4][5]. - Their first visit to the Great Wall was in 1984 at the ancient northern pass of Gubeikou, where they relied on limited transportation options to reach the Wall [4][5]. - The father-son duo gained recognition in the Great Wall exploration community and made significant contributions to identifying the locations of historical photographs related to the Great Wall [5]. Group 2: Research and Discoveries - The Yan family successfully identified the location of a historical photograph taken by photographer Sha Fei in 1938, which had remained a mystery for years, by analyzing architectural details such as wall materials and window configurations [5][6]. - They developed a methodology termed "morphology," focusing on the physical characteristics of the Great Wall rather than relying on vague geographical names, which allowed them to uncover more secrets of the Wall [6]. - Their research efforts led to the publication of "Great Wall Morphology Atlas," which aims to provide a comprehensive understanding of the Great Wall's defensive architecture and aesthetic beauty [6]. Group 3: Personal Experiences and Legacy - The article recounts personal anecdotes from the Yan family's explorations, including a memorable winter encounter in 1987 when they sought refuge from a snowstorm [6]. - The father-son duo emphasizes the importance of documenting the lesser-known aspects of the Great Wall, aiming to inspire future generations to appreciate its rich history and intricate details [6].

Group 1 - The report discusses ETF rotation, which involves switching between different ETFs based on market conditions to adjust investment portfolios across various asset classes, industries, or regions [6][7][8] - The core logic of ETF rotation is to dynamically adjust the ETF portfolio to seek returns that exceed those of passive single-asset holdings [6][8] - The report introduces a methodology using stock patterns as raw data to synthesize ETF signals for rotation strategies, allowing for a comparative analysis of different ETFs [1][16] Group 2 - Three trading strategies based on historical data backtesting are proposed: fixed time point rebalancing, daily rebalancing, and a buy-and-hold exit strategy when signals disappear [2][35] - The buy-and-hold exit strategy is identified as the most effective, leveraging the characteristics of signal patterns while respecting low-frequency turnover rules [2][35] - The report provides performance metrics for each strategy, indicating that all strategies can outperform the Wind Mixed Equity Fund Index [2][35] Group 3 - The fixed time point rebalancing strategy shows varying annualized returns based on the number of ETFs selected, with the best performance observed when selecting six ETFs [17][20] - The daily rebalancing strategy also demonstrates performance metrics, with optimal results when selecting four ETFs, balancing risk and transaction costs [21][28] - The buy-and-hold exit strategy yields the highest annualized returns when selecting four ETFs, indicating that more is not always better in ETF rotation [29][31] Group 4 - The report emphasizes the importance of obtaining morphological signals through an API, allowing users to access comprehensive shape definitions and daily signals [36][37] - This API facilitates the replication of the index timing strategy, industry rotation strategy, and the ETF rotation strategy discussed in the report [36][37]