The South Korean tech company said Tuesday that its fourth-quarter operating profit is set to plunge nearly 30% from a year earlier. It blamed the sharp drop on "lackluster demand" for its memory chips and "intensifying competition" in the smartphone industry. Samsung's guidance comes after Apple (AAPL) set off alarm bells last week by warning that it will sell fewer iPhones than previously expected, mainly because of disappointing demand in China amid an ongoing trade war with the United States.