一种V/U频段零中频发射信道小型化设计

针对V/U频段,提出了一种宽带发射机的前端设计方法,其中包括射频信道设计、频率合成器的设计以及基带电路设计。鉴于小型化的设计思想,射频前端采用零中频发射机架构,通过合理的滤波、放大等信号处理,输出1 dB压缩点为16 dBm。频率合成器采用集成VCO的锁相环芯片ADF4351,为满足高速跳频通信体制,采用兵乓环高速换频,实现单边带相位噪声优于-125 dBc/Hz@100 kHz,频率切换时间小于10μs。基带电路采用正交调制器LTC5598和12位双通道DA转换器AD9716,可实现最大带宽为40 MHz的I/Q双路同时调制。通过FPGA或DSP基带处理,可广泛用于V/U小型化发射机设计。     

The corrosion of mild and stainless steel in alkaline anaerobic conditions representing the Belgian “supercontainer” concept and the Swiss L/ILW repository

Deep geological repositories for radioactive waste contain metallic materials, either used to construct disposal canisters or as low-/intermediate-level waste (L/ILW). The safety relevance of corrosion is linked to canister lifetime in the former case and gas generation in the latter. More specifically, the Belgian “supercontainer” concept envisages mild steel for the used fuel disposal canister, and in the case of the Swiss L/ILW repository, mild steels are the largest metallic waste component due to the decommissioning of civilian power-generating facilities. For these circumstances, the corrosion environment is dominated by the chemistry of cement, which is used as buffer or backfill material. The corrosion behaviour of mild steel in anoxic environments was studied through the analysis of the hydrogen end-product. Hydrogen analysis was conducted by periodically purging the cell head-space and analysing the gas using a solid-state hydrogen sensor. While this method is limited to providing only uniform corrosion rates averaged over periods of time, ranging from weeks to months, it provides excellent resolution and sensitivity. The test cell environments were matched against the anticipated Belgian high-level waste and Swiss L/ILW repository environments, and also against experiments that have been conducted by other researchers for comparative purposes. Samples were exposed to synthetic cement pore waters, representing fresh and degraded cement. In young cement waters, the formation of initial corrosion products resulted in steel wire corrosion rates of the order of µm/year, which, at 80°C rapidly declined to ∼10 nm/year. In contrast, SA516 grade 70 steel plate corroded much more slowly under similar conditions. In aged cement waters, initial corrosion rates were higher but declined faster towards a longer-term rate of ∼10 nm/year. 316L stainless steel, embedded in cementitious material, corroded at a rate of <1 nm/year at 50°C.     

AU1100用三路开关型稳压器的设计

嵌入式微处理器AU1100用三路开关型稳压器以LT1940、LTC3404为核心.LT1940由7～25VDC输入产生3.3V和5V电压,分别为串口等外设和USB主机口等供电.3.3V作为另路输出电压接LTC3404主电源引脚,产生1.8V电压为嵌入式内核供电.电感器、输入输出电容等外围电子元件经计算后按需求选择.     

基于LTC4000 的锂电池充电模块

为了达到高效、便捷、低成本的充电目的,设计一款基于LTC4000的锂电池充电模块。该模块以三阶段充电法为设计理念,硬件方面选用 MSP430系列单片机作为主控芯片,具有电压、电流调节模块实现稳定输出,软件方面通过MODBUS协议和RS485物理接口实现与上位机的通信,并制作PCB电路板对该模块进行验证。实验结果证明：该系统结构简单、携带方便、实用性强,上电后能迅速达到稳定状态,有广阔的市场前景。     

Various strategies for reducing Nox emissions of biodiesel fuel used in conventional diesel engines: A review

Energy demand, decreasing fossil fuel reserves, and health-related issues about pollutants have led researchers to search for renewable alternative fuels to either partially or fully replace fossil fuels. Among many alternative fuels, biodiesel became one of the most popular choices due to similar properties to that of conventional diesel. Biodiesel produces slightly lower brake thermal efficiency compared to that of conventional biodiesel, but has an advantage of reduced emissions of CO₂, CO, HC, and smoke. However, biodiesel shows higher NOx emission which, when used in increased biodiesel market, may become a serious problem. Various strategies were attempted by different researcher to reduce NOx emissions. In this paper, various strategies, adapted for reducing NOx emissions of biodiesel fuel used in diesel engines for automobile applications, are reviewed and discussed. The strategies are grouped into three major groups, namely combustion treatments, exhaust after-treatments, and fuel treatments. Among various strategies discussed, fuel treatments, such as low temperature combustion, mixing fuel additives and reformulating fuel composition, reduce NOx emission without compromising other emission and performance characteristics and they seem to be promising for future biodiesel fuel.     

Assessing the performance of long-term care information systems and the continued use intention of users

The needs of long-term care (LTC) have increased substantially worldwide. In particular, Taiwanese society has experienced an increasing aging population because of the sharp decline in the birth rate and advanced medical technology. Some LTC facilities have introduced information technologies to satisfy the substantial demand. Compared with the high level of informatization observed at Taiwanese hospitals, LTC facilities still exhibit low informatization levels despite belonging to the same industry. Therefore, this study evaluated the system use performance and continued use intentions of the long-term care information system (LTCIS) by applying the well-known theories of the task-technology fit, system satisfaction, and postacceptance continuance models used in information systems area. The results showed that users’ assessment of whether the LTCIS fulfilled their work and task needs primarily depended on the system quality, locatability of data, timeliness, ease of use, and system-user relationship. These factors also exerted a crucial influence on system use performance and user satisfaction. Moreover, the system use performance and user satisfaction further affected intentions of continued use.     

光发射机波长的调谐与精确控制

对有线电视网络中光发射设备波长稳定的重要性作出论述，并根据激光器波长与温度的关系，提出了波长微调与精确控制的方法。推荐Linear公司的LTC1923作为激光器温度控制的主电路，有效地解决了这一问题，同时较为详细地描述了这一电路的工作原理。     

高效LED驱动器LTC3219及其应用

高集成度9通道LED驱动器LTC3219具有高效、低噪声、可进行数字编程等特点。文中介绍了LTC3219的工作原理及主要功能,同时给出了LTC3219的一个典型应用电路。     

用高压I~2C电流和电压监视器进行测量

采用分立元器件和其他电源监视器的传统实施方法在复杂性、功能或性能方面往往达不到要求,LTC4151提供一种简单但非常有效的方法来监视电流、电压和温度.本文介绍了一个通用电源监视器LTC4151如何应对多种电源监视应用的功能需求.     

Liquid penetration length of heptamethylnonane and trimethylpentane under unsteady in-cylinder conditions

While strategies employing early or late direct-injection of fuel can improve emissions, they also can lead to impingement of liquid-phase fuel on the piston and/or cylinder wall due to low in-cylinder temperatures and densities during the injection event. Previous work has shown that liquid-phase fuel films formed in this way can lead to pronounced degradations in efficiency and emissions. To avoid these problems, a quantitative understanding of fuel-property effects on the liquid penetration length is needed, and this understanding must include conditions where in-cylinder thermodynamic conditions and the injection rate vary with time. This work reports liquid penetration lengths measured in an optical engine under such time-varying conditions. Diagnostics included laser light scattering for measurement of the liquid length and conventional pressure-data acquisition for heat-release analysis. Unsteady liquid penetration was characterized for different injection timings, injection pressures, intake-manifold pressures, and fuel volatilities to gain an understanding of the relative importance of these factors. Fuel volatility was studied by using two fuels, 2,2,4,4,6,8,8-heptamethylnonane (HMN) and 2,2,4-trimethylpentane (TMP), which have very different volatility characteristics. Measured liquid lengths changed as in-cylinder conditions changed, with increasing temperature and density during the compression stroke causing a decrease in liquid length, and decreasing temperature and density during the expansion stroke causing an increase in liquid length. Intake-manifold pressure and fuel volatility were found to be primary factors governing liquid length. Heat loss from the charge gas to the engine and local charge cooling due to fuel vaporization were found to have a secondary influence on liquid length. Injection pressure was found to have little effect.