虽然他们已遭受惨重损失，但还是不肯认输。

Although they had suffered heavy losses, they refused to concede defeat.

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虽然他们已住在同一屋顶下多年，他们不知道每一其他。

Though they've lived under the same roof for many years, they don't know each other.

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虽然他们已寻获好几种有希望的材料，但要做出实际的装置，使其性能符合要求，却仍然是个挑战。

Although several promising materials had been identified, achieving acceptable performance in practical devices proved to be a challenge.

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