In natural environment, sound signals often occur with background noise.

In the construction process, engineering changes often occur.

建设项目建设过程中，常会发生工程变更。

Geological diseases often occur in the civil construction.

地质病害在土建施工中是经常发生的。

Thus, claims are often occur during construction of a project.

因此，在工程的实施过程中，索赔是经常发生的。

Hepatitis B, C and D usually occur as a result of parenteral contact with infected body fluids.

发生乙型、丙型和丁型肝炎通常是由于通过非肠道途径接触了受感染的体液。

They usually occur during stressful moments, such as when a person is in danger.

它们通常出现在压力大的时候，比如说当人处于危险中。

They usually occur along the boundaries of the thin plates that cover the Earth like an egg shell.

地震一般都在较薄的板块边缘沿线发生，而较薄的板块对地球而言就像鸡蛋壳一样。

In blasting engineering work, the influence of complicated geological conditions whiCh usually occur on blasting effect comes in many ways.

定向爆破工程中，爆区地质条件往往很复杂，因此对爆破效应的影响也是多方面的。

Osteoporosis is usually occur concomitantly with arterial calcification in elderly.

众所周知老年患者发生骨质疏松的同时常常伴发血管钙化。

BACKGROUND: Vascular complications usually occur in diseases related to obesity such as primary hypertension or diabetes.

背景：原发性高血压、糖尿病等肥胖相关性疾病往往出现血管并发症，活血化瘀法治疗肥胖症有一定疗效，据此推测肥胖与血瘀证可能相关。

Tunnel projects usually occur in city where high-rise building and elevated bridge etc have badly concentrated.

地铁工程建设多滞后修建于高层建筑、高架桥梁等已高度密集的城市环境中。

Terrible things usually occur at midnight.

可怕的事情通常在午夜发生。

The mutations usually occur in mucous malignant cancer and the mutation rate is increased significantly.

polβ基因突变多发生在粘膜性恶性肿瘤，并且突变发生频率也相对较高。

The breakthrough of gas usually occur during low permeability reservoir development, that lead to recovery efficiency fall.

低渗透油藏注气开发极容易发生气窜，导致采收率降低。

They usually occur in high stakes situations, where people have something to lose or gain.

微表情通常会在人们经历得失、情势危急的时候出现。

Faulf of electric equipments usually occur in their use.

电气设备使用中经常会出现故障。

Small precursory events usually occur before strong instability involving the intersecting faults.

涉及交叉断层的较大失稳事件发生前常出现前兆性小事件。

The events callbacks usually occur at the time of parsing.

事件回调通常在进行解析时发生。

The respiratory behaviors usually occur when they are in the middle of water.

母仔豚呼吸行为多发生在夹江中心水域。

These two kinds of lesions usually occur within 3 months after birth.

婴儿湿疹和婴儿脂溢性皮炎好发于出生后3个月以内的婴儿，后者可能是由于母体雄性激素的影响。

This class of problems usually occur in many scientific and engineering fields.

此类问题时常出现在许多科学与工程的研究领域内。