每次过节，回国前总是为礼品发愁。这回俺发现了理想礼物。
有点儿空儿的时候，理工男喜欢自己动手给自己造玩具 （见 【1】和 【2】）。但这个东东：Burnout 恒温咖啡/茶/热水杯（是的，不仅保温： 是恒温！） 是俺从网上买的。
大概是这一两年刚出的最新产品，“魔杯”让俺喜爱上瘾，办公室家中各有一个，现在很少离手：100度 （C） 的水倒入，1-2 分钟内降至最宜喝的 60C，并恒温在此五六个钟头。一杯在手，I can have a sip of coffee, tea, or hot water of perfect temperature, whenever and wherever I wish. 真的会上瘾的。
Amazan 上有卖。查 ”Burnout mug“ 就能找的。
俺找了个包，出门到处都带着。还送给几个给朋友和同事做礼物，用过的都很喜爱 。我2018年底送了秘书一个，结果圣诞时她给她的老爹老妈老弟一人买了一个。Amazon 的 Customer Review 也很好：
杯子的密秘是用了变相材料层吸温恒温。他们的网站上有解释 （Amazon上还有另一品牌的，好象具相同功能，但那个要价149刀，还需要电池电源来保温恒温。这个Burnout什么都不用）。理工男觉得Burnout的工作原理应是如下：
From their website, it is clear that a Burnout mug is firstly a normal thermos mug, but with an added layer filled with phase-changing material (PCM). Therefore, so far as keeping the heat in, it functions exactly like a normal thermos mug.
However the added PCM layer will firstly absorb the excessive heat quickly to cool the beverage down to optimal drinking temperature, and then keep this amount of heat within it through changing its state (or change of phase, like when water boils to absorb heat to become steam).
Acorrding to thermodynamics, this amount of heat cannot just disappear, so it keeps the beverage at the constant temperature by gradualy releasing the heat back to the beverage - kind like having a built-in heater - untill all heat is used up and the PCM then goes back to its original state.
Scientifically, therefore, a Burnout mug firstly cools the drink down quickly to the optimal drinking temperature, and then keeps the beverage at this temperature for hours, all done "naturally" without having to use batteries, power-supplies, and APPs to regulate the temperature.
Economically, it helps reduce costs of beverage by eliminating waste due to thrown-away cold coffee/tea.
Environmental, in the long run it should help reducing food waste which is a significant issue global-wise.
Finally rom an engineering point of view: simple, elegant, and very clever!
