A new opera house in Algeria. Traffic lights in Liberia's capital city. A malaria prevention centre in Mozambique. These are some of the aid programs China has financed in recent years in Africa. A new study and database released by the Center for Global Development in Washington and AidData, a research group at William and Mary College, has turned up details on 1,673 Chinese development projects worth $75 billion in 50 African countries between 2000 and 2011.The data's release comes after years of China refusing to release details of its aid activities. That lack of transparency has worried some aid critics, who say China's aid to Africa is growing by leaps and bounds as the continent has become a significant source of oil and mining riches. China, which like western countries use aid to bolster influence in Africa's 54 countries, is often criticized for offering aid without demanding local governments improve human rights.