discharged. Although an ideal capacitor would reach zero volts after discharge, real capacitors develop a small voltage from time-delayed dipole discharging, a phenomenon that is also called dielectric relaxation, "soakage" or "battery action". Dielectric absorption can cause a problem in circuits where very small currents are used, such as long-time-constant integrators or sample-and-hold circuits. However, in most applications where tantalum electrolytic capacitors are supporting power supply lines, dielectric absorption is not a problem. Reliability and life time Reliability (failure rate) The reliability of a component is a property that indicates how well a component performs its function in a time interval. It is subject to a stochastic process and can be described qualitatively and quantitatively; it is not directly measurable. The reliability of electrolytic capacitors are empirically determined by identifying the failure rate in production-accompanying endurance tests, see Reliability engineering#Reliability testing. The reliability normally is shown in a bathtub curve and is divided into three areas: Early failures or infant mortality failures, constant random failures and wear out failures. Failure types included in the total failure rate are short circuit, open circuit, and degradation failures (exceeding electrical parameters). The reliability prediction is generally expressed in a failure rate λ, abbreviation FIT (failures in time). This is the number of failures that can be expected in one billion (109) component-hours of operation (e.g. 1000 components for 1 million hours, or 1 million components for 1000 hours which is 1 ppm/1000 hours) at fixed working conditions during the period of constant random failures. These failure rate model implicitly assume the idea of "random failure". Individual components fail at random times but at a predictable rate. The standard operation conditions for the failure rate FIT are 40 °C and 0.5 UR. The reciprocal value of FIT is mean time between failures (MTBF). For tantalum capacitors, often the failure rate is specified at 85 °C and rated voltage UR as reference conditions and expressed as per cent failed components per thousand hours (n %/1000 h). That is "n" number of failed components per 105 hours or in FIT the ten-thousand-fold value per 109 hours. For conditions other than the standard operation conditions 40 °C and 0.5 UR, for other temperature and voltage applied, for current load, capacitance value, circuit resistance, mechanical influences and humidity, the FIT figure can recalculated with acceleration factors standardized for industrial or military contexts. For example, higher temperature and applied