Samsung will unveil its new Galaxy S10 phone, which is expected to have a folding screen that can double its size, on Wednesday. A splashy debut might help the company shake off some winter blues — last month, Samsung announced earnings had fallen in the fourth quarter of 2018, and said it expected overall earnings to decline this year. Sales of personal devices like Samsung’s are slowing, and both the economic slowdown in China and the U.S.-China trade war has weakened demand for memory chips, of which it is also a leading manufacturer globally. Will a folding screen make a difference?