1～2 月，工程机械行业基本面仍未出现明显改观，行业投资再次出现同比负增长；2 月份，八大工程机械产品总销量创下2011 年以来的历史新低；尽管生产企业去库存已进入尾声，但企业坚持以销定产，加之春节因素影响，主要产品产量同比大幅下滑。

2015 年1～2 月，家电行业受到春节元旦礼品性和冲动性消费需求影响，加之“价格战”的延续，行业销量回暖；家电企业排产力度大幅收缩使得库存压力已明显缓解。

The global population is projected to reach 9 billion by 2050. This rise in population will lead to an increase in demand for wood for houses, furniture, fuel, pulp, and other needs. This, in turn, will increase the demand for forest equipment such as chainsaws. They are not only used by loggers but also by end-users at home for gardening, sculptors for sculpting wood or ice, carpenters, and others. Chainsaws are of two types: gas chainsaws and electric chainsaws. The demand for electric chainsaws are increasing worldwide as they are easy to use, lightweight, ecofriendly, and less noisy

Apheresis is an invasive process that involves the separation of platelets, red blood cells, plasma, and other blood components from whole blood. A donor or patient's blood is passed through an apheresis equipment or a blood cell separator. The equipment separates specific blood components from the blood via centrifugation. The remaining blood components are transfused back into the donor or patient. Along with separation technologies, apheresis also involves the use of devices and disposables for centrifugation and membrane filtration. Apheresis equipment can be manual or automated.

Elevators and escalators are installed in commercial, residential, and mixed-used buildings; IT parks, hotels, restaurants, and retail outlets. They are also installed in public places to improve vehicle parking management. The elevator and escalator market in Canada will be driven by growth factors that include the growth in construction of high-rise buildings. More than 40 high-rise buildings are planned to be constructed in the country by 2022. With the development of the high-rise construction market, a number of new high-rise buildings, especially for residential purposes, are planned to be constructed during the forecast period.

Motive lead-acid batteries, also known as traction batteries, provide motive power for small transport vehicles such as forklifts, golf carts, railroads, and mining vehicles. These motive devices generally include small hand-operated trucks, pallet-jacks, and forklifts. The most common battery-operated forklifts are used for indoor transportation in warehouses, and in the manufacturing and material handling industries.

在多电平变换器研究领域,三电平中点钳位逆变器目前是一种研究比较广泛的一种拓扑结构,但是此拓扑结构容易造成中点电压偏移问题。基于理论上虚拟空间矢量的调制方法可以实现分压电容中点电压平衡控制,因此,为增强中点电压平衡的控制效果,提出调节虚拟中矢量中点电流和分配正、负小矢量作用时间的中点电压平衡控制方法。相对虚拟空间矢量脉宽调制算法和混合式调制算法来说,所采用的可变虚拟空间矢量控制算法简单、实用,能实现三电平NPC变换器中点电位平衡控制。 

针对直流锅炉主蒸汽温度控制系统复杂,控制链跨度大的问题,在分析了主汽温控制系统特点的基础上,提出一种基于逆向传递策略的串级系统网络化预测控制方法,并采用遗忘因子递推最小二乘法(RLS)对子系统进行在线辨识,适应直流锅炉变工况需要。为了使喷水减温具有较大的调整范围,通过主汽温导前区在线辨识结果实现对逆向传递策略中设定值的设计;并用预测控制的约束条件,保证中间点温度和各级过热器出口具有足够的过热度。将该方法应用于电厂过热汽温控制系统进行仿真研究,结果表明该方法能较好地适应对象特性的变化,且控制效果明显优于常规串级控制系统。 

对于三电平逆变器中点电压低频振荡问题,传统正弦脉宽调制(sinusoidal pulse width modulation,SPWM)控制一般不具有中点电压平衡控制作用。该文基于不连续脉宽调制(discontinuous pulse width modulation,DPWM)的基本原理,提出了一种半周期动态调节的DPWM(dynamic half carrier-cycle regulative DPWM,DHCR-DPWM)中点电压平衡控制方法。该DHCR-DPWM控制方法通过控制载波周期内某相桥臂开关不动作,使得正负小矢量作用时间相等,实现对中点电压低频振荡的抑制,控制中点电压平衡。与传统SPWM控制相比,该方法能够提高输出波形质量和系统效率。在基于STM32F407-CPLD的二极管中点箝位型三电平逆变器实验平台上进行了实验验证,实验结果验证了理论分析的正确性和方法的有效性。 

针对目前杆塔接地电阻测量方法效率低下、精度不高、适应性不强的问题,提出了一种不断开接地引线、多频扫描式杆塔接地电阻的测量方法,其基本原理是在不断开接地引线的条件下,向杆塔接地体中注入频率可调的激励电流,测取不同注入电流频率下被测杆塔的接地电阻值,依据测量数据采用数据拟合方法计算被测杆塔接地电阻的精确值。给出了多频扫描式杆塔接地电阻的准确测量模型,并进行了准确测量时影响因素分析及注入激励电流频率范围的确定方法。同时,构建多频扫描式杆塔接地电阻测量系统进行实地测量实验。结果表明:所提出的方法可以实现不断开接地引线杆塔接地电阻的准确测量,比现有测量方法具有更高的测量精度和更好的实用性。