4 sentences for 集中 (jí​zhōng — concentrated)

1. 人口主要集中在沿海大城市。

   rén​kǒu zhǔ​yào jí​zhōng zài yán​hǎi dà chéng​shì.

   The population is mainly concentrated in large coastal cities.

   Source: Dong Chinese Dictionary

2. 原子的质量几乎全部集中在核上。

   yuán​zǐ de zhì​liàng jī​hū quán​bù jí​zhōng zài hé shàng.

   Almost all the mass of an atom is concentrated in the nucleus.

   Source: Dong Chinese Dictionary

3. 北方地区的冬季集中供热通常持续四个月。

   běi​fāng dì​qū de dōng​jì jí​zhōng gōng​rè tōng​cháng chí​xù sì gè yuè.

   Centralized heating in northern regions usually lasts for four months in winter.

   Source: Dong Chinese Dictionary

4. 这两个国家目前的交流主要集中在民间层面。

   zhè liǎng gè guó​jiā mù​qián de jiāo​liú zhǔ​yào jí​zhōng zài mín​jiān céng​miàn.

   Current exchanges between the two countries are mainly focused at the non-governmental level.

   Source: Dong Chinese Dictionary