Acoustic Impedance in Ultrasonic Reflection

Exothermic welding, also known as thermite welding, is a technique that uses the superheated molten metal from an aluminothermic reaction to create a strong, permanent molecular bond between metal components. The process is self-contained, requiring no external power source. It is most famously used to join sections of railway track into continuous welded rail, creating a smoother and more durable track.

Oxy-fuel cutting, or flame cutting, severs ferrous metals by a rapid, exothermic oxidation process. First, a preheating flame raises the steel's surface to its kindling temperature (approx. 870 °C or 1600 °F). A high-pressure jet of pure oxygen is then directed at the spot, initiating a chemical reaction, [latex]3Fe + 2O_2 \rightarrow Fe_3O_4[/latex], which forms molten iron oxide (slag) and releases heat.

Gas cylinders for oxy-fuel welding store gases or other industrial or medical gases, at very high pressures. A pressure regulator is essential to reduce this to a safe, usable working pressure. A two-stage regulator performs this reduction in two steps, providing a highly constant delivery pressure even as the cylinder pressure drops with use. This ensures a stable flow, thus a stable flame for consistent weld quality.

自働化（Jidoka）通常被翻译为“自动化”或“人性化的自动化”，是丰田生产系统的支柱之一。它授权任何机器或工人在检测到异常或缺陷时立即停止整条生产线。这可以防止大量生产缺陷产品，并立即发现问题，从而分析根本原因并找到永久性解决方案。

生产间隔时间（Takt time）是指为满足客户需求而生产产品所需的最长时间。它的计算方法是用净可用生产时间除以该时间段内的客户需求量。计算公式为：[latex]T = \frac{T_a}{D}[/latex]，其中，T 为工时，Ta 为净可用时间，D 为客户需求。

高效微粒空气 (HEPA) 过滤器和超低微粒空气 (ULPA) 过滤器是洁净室的关键组件。HEPA 过滤器必须能够去除至少 99.97% 直径为 0.3 微米 (µm) 的空气悬浮颗粒。ULPA 过滤器效率更高，能够去除 99.999% 直径为 0.12 µm 或更大的颗粒。它们通过拦截、撞击和扩散相结合的方式发挥作用。

一个经验公式，用于描述电池的可用容量如何随着放电率的增加而减少。该定律表示为 [latex]C_p = I^k t[/latex]，其中 [latex]C_p[/latex] 是一安培放电速率下的容量，[latex]I[/latex] 是放电电流，[latex]t[/latex] 是放电时间，[latex]k[/latex] 是针对电池类型的普克特常数。它量化了高负载时的低效率。

Oxy-acetylene welding uses a flame produced by the combustion of acetylene ([latex]C_2H_2[/latex]) with pure oxygen. The reaction occurs in two stages. The primary reaction in the inner, white-hot cone is incomplete, producing carbon monoxide and hydrogen: [latex]2C_2H_2 + 2O_2 \rightarrow 4CO + 2H_2[/latex]. These hot gases then react with atmospheric oxygen in the outer envelope, completing the combustion.

The properties of an oxy-acetylene flame are controlled by the volumetric ratio of oxygen to acetylene. A neutral flame (ratio ≈ 1.1:1) is standard for steel welding. A carburizing or reducing flame (ratio 1.1:1) has excess oxygen, is hotter, and is used for braze-welding.

Temper embrittlement is a reduction in the toughness of certain alloy steels caused by holding them in, or slowly cooling them through, a specific temperature range (approximately 375–575 °C). This phenomenon is driven by the segregation of impurity elements (e.g., phosphorus, tin, antimony) to the grain boundaries, which weakens the cohesion between grains and promotes intergranular fracture.

For materials that do not have a distinct yield point on their stress-strain curve, like aluminum or high-strength steel, 'proof stress' is the engineering equivalent. It is defined as the stress required to produce a small, specified amount of permanent (plastic) deformation, typically 0.2% of the original gauge length. This value, [latex]\sigma_{0.2}[/latex], is used in design calculations as the material's practical elastic limit.

点状腐蚀是一种局部腐蚀，会在金属上形成小孔或 "凹坑"。点蚀是最具破坏性的腐蚀形式之一，因为它难以检测、预测和设计。点蚀只占总质量损失的一小部分，就能导致结构发生灾难性故障。

Liquid metal embrittlement is a phenomenon where a normally ductile solid metal experiences a severe loss of ductility and fails in a brittle manner when wetted by a specific liquid metal while under tensile stress. The failure is often catastrophic and rapid. The mechanism involves the liquid metal atoms adsorbing at a crack tip, which reduces the cohesive strength of the solid's atomic bonds.

准时制 (JIT) 是一种生产策略，旨在通过仅在生产过程中需要时接收货物来提高效率并减少浪费，从而降低库存成本。这种方法需要精准的预测和高度协调的供应链。目标是在正确的时间、正确的地点、以正确的数量获得正确的物料。