提出一种谐振软开关耦合电感高增益DC-DC变换器,通过引入辅助网络,将Boost变换器的输出二极管替换为开关管,实现全部开关管的零电压导通(ZVS)和二极管的零电流关断(ZCS),并降低开关管的开关损耗,消除二极管的反向恢复问题.同时,变换器输出端为三个输出单元串联,提高变换器的电压增益,避免变换器工作于极限占空比,在实现高升压增益的同时降低开关管电压应力.因此可选取低电压等级、低导通电阻的MOSFET,以提高变换器效率.倍压电容与耦合电感的漏感谐振,可减小开关管关断时刻电流,降低开关损耗,进一步提高变换器效率.研究变换器的工作原理和工作特性,分析开关管ZVS条件.设计制作一台160W的实验样机,实验结果验证了理论分析的正确性.

The dynamics of aboveground biomass (AGB) are driven by both climate variation and anthropogenic modification, however, few studies have evaluated the relative importance of these two drivers, especially in a heterogeneous landscape. Taking the Mongolian Plateau as a case study and employing the vegetation optical depth retrieval as a proxy of AGB, this study aimed to determine the relative importance of climatic and anthropogenic drivers on the dynamics of AGB in Mongolia (ML) and the Inner Mongolia Autonomous Region (IM), China. Spatial panel data model specific to each agro-ecological zone was employed to fulfill the task. The results revealed that: (1) Since the socio-institutional transition in the early 1990s, AGB declined in most parts of the grazing zone of Mongolia. The reduction of precipitation, the rise of temperature and the intensification of livestock grazing were the major drivers behind it. Ranked by their relative importance, the order in the grazing zone with relatively humid climate was: Precipitation ≈ temperature > livestock grazing; the order in the grazing zone with relatively arid climate was: Precipitation > temperature > livestock grazing; (2) Since the implementation of a series of ecological restoration programs in the early 2000s, AGB increased in most parts of the grazing zone of IM, and the increase of precipitation was the dominant driver behind it; (3) Since the early 2000s, AGB increased in most parts of the grazing-farming zone of IM. The increase of precipitation, the decline of temperature and the intensification of grain production were the major drivers behind it. Ranked by their relative importance, the order was: Precipitation > grain production > temperature; (4) Since the early 2000s, AGB increased in most parts of the farming zone of IM. The increase of precipitation and the intensification of grain production were the major drivers behind it. Ranked by their relative importance, the order was: Grain production > precipitation.

Ongoing global warming has triggered extreme climate events of increasing magnitude and frequency. Under this effect, a series of extreme climate events such as drought and increased rainfall during the El Nino Southern Oscillation (ENSO) are expected to be amplified in the coming years. Adequate mapping of regions with climate-sensitive vegetation and its associated time lag is required for appropriate mitigation planning to avoid potential negative ecological impacts towards vegetation. In this study, ENSO and climate indicator time series data, for example, Multivariate ENSO Index (MEI) and Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS) data for rainfall were linked with long-term time series vegetation proxies from remote sensing (RS proxies). ENSO- and rainfall-sensitive areas were identified from each RS proxy using the bivariate Granger test, and the areas identified by multiple RS proxies were taken to identify climate-sensitive regions in Indonesia. Of the biome types in Indonesia, savanna was the most sensitive, with approximately 53% of the total savanna area in Indonesia shown to be sensitive to ENSO and rainfall by two or more RS proxies. Rolling correlation analysis also found that the ENSO effect on the vegetation region after rainfall was positively correlated with the RS proxies with a time lag of +5 months. Therefore, rainfall can be taken as a proxy of the effects of ENSO on the temporal dynamics of sensitive vegetation regions in Indonesia.

Based on soft-switched boost converter, a soft-switched DC-DC converter with high voltage gain is proposed by introducing a Flyback-cell with coupled inductor. The proposed converter achieves high voltage gain, reduces switch stress, and recycles the energy stored in the transformer leakage inductor. Thus the proposed converter improves the efficiency of converter and reduces the cost by using low voltage stress MOSFET. Zero voltage switch (ZVS) turn-on of switches and the zero current switch (ZCS) turn-off of diodes are achieved, which improve the efficiency of the converter. The operating characteristics of converter, the duty ratio loss of converter, and the stress of switching devices are analyzed in this paper. Experimental results of a 160W prototype verify the analysis results of the proposed converter.

BACKGROUND:We conducted a meta-analysis evaluating the efficacy and safety of acupuncture compared to disease-modifying antirheumatic drugs in patients with ankylosing spondylitis.METHODS:Four databases including Pubmed, EMBASE, Cochrane library, and ISI Web of Science were searched in December 2014, taking also the reference section into account. Randomized controlled trials that aimed to assess the efficacy of acupuncture therapy were identified. The inclusion criteria for the outcome measurements were the clinical effect, ESR, occipital wall test, chest expansion, CRP and finger ground distance. Finally, six studies met these inclusion criteria. Two reviewers screened each article independently and were blinded to the findings of each other.RESULTS:We analyzed data from 6 RCTs involving 541 participants. Acupuncture therapy could further improve the clinical effect (OR = 3.01; 95% CI, 1.48-6.13; P = 0.002) and reduce ESR level (SMD = -0.77; 95% CI, -1.46 to -0.08; P = 0.03) compared to DMARDs; a combination of acupuncture and DMARDs could further improve clinical effect (OR = 3.20, 95% CI, 1.36-7.54; P = 0.008), occipital-wall distance (SMD = -0.84; 95% CI, -1.37 to -0.31; P = 0.002), chest expansion (SMD = 0.38; 95% CI, 0.16-0.60; P = 0.0009), and finger-ground distance (SMD = -0.48; 95% CI, -0.87 to -0.09; P = 0.02) as compared to DMARDs treatment alone.CONCLUSIONS:Our findings support that acupuncture therapy could be an option to relieve symptoms associated with AS. These results should be interpreted cautiously due to the generally poor methodological qualities of the included trials.

A small set of isoprenoid bisphosphonates ethers has been tested in the K562 chronic myelogenous leukemia cell line to determine their impact on isoprenoid biosynthesis. Five of these compounds inhibit geranylgeranyl diphosphate synthase (GGDPS) with IC50 values below 1μM in enzyme assays, but in cells their apparent activity is more varied. In particular, the isomeric C-geranyl-O-prenyl and C-prenyl-O-geranyl bisphosphonates are quite different in their activity with the former consistently demonstrating greater impairment of geranylgeranylation in cells but the latter showing greater impact in the enzyme assays with GGDPS. Together, these findings suggest an organized binding of these inhibitors in the two hydrophobic channels of the geranylgeranyl diphosphate synthase enzyme.

The N-oxide derivatives of [2-(3-pyridinyl)-1-hydroxyethylidene-1,1-phosphonocarboxylic acid (or PEHPC) and [2-(3-pyridinyl)-1-ethylidene-1,1-phosphonocarboxylic acid (or PEPC) have been prepared and evaluated for their activity against several enzymes which utilize isoprenoids. The parent pyridines are known inhibitors of GGTase II, but the N-oxide derivatives show no improvement in biological activity in assays with the isolated enzyme. However, the PEHPC N-oxide did induce significant accumulation of intracellular light chain in myeloma cells, consistent with inhibition of Rab geranylgeranylation.

We report wavelength-division-multiplexed transmission of ninety 128-Gb/s polarization-multiplexed quadrature-phase-shift-keyed channels in a seamless 73 nm band over 60 × 100 km of ultra-large-area fiber. Co- and counter-pumped all-Raman amplification in the fiber spans, single-stage discrete Raman amplifiers, and broadband wavelength selective switch and channel equalizer were utilized to achieve optical signal-to-noise-ratio margin of more than 3 dB after 6000 km transmission of the 9 Tb/s capacity.

A full-bridge secondary dual-resonant DC DC converter using the asymmetrical pulse-width modulated (APWM) strategy is proposed in this paper. The proposed converter achieves zero-voltage switching for the power switches and zero-current switching for the rectifier diodes in the whole load range without the help of any auxiliary circuit. Given the use of the APWM strategy, a circulating current that exists in a traditional phase-shift full-bridge converter is eliminated. The voltage stress of secondary rectifier diodes in the proposed converter is also clamped to the output voltage. Thus, the existing voltage oscillation of diodes in traditional PSFB converters is eliminated. This paper presents the circuit configuration of the proposed converter and analyzes its operating principle. Experimental results of a 1 kW 385 V/48 V prototype are presented to verify the analysis results of the proposed converter.

When inhibitors of enzymes that utilize isoprenoid pyrophosphates are based on the natural substrates, a significant challenge can be to achieve selective inhibition of a specific enzyme. One element in the design process is the stereochemistry of the isoprenoid olefins. We recently reported preparation of a series of isoprenoid triazoles as potential inhibitors of geranylgeranyl transferase II but these compounds were obtained as a mixture of olefin isomers. We now have accomplished the stereoselective synthesis of these triazoles through the use of epoxy azides for the cycloaddition reaction followed by regeneration of the desired olefin. Both geranyl and neryl derivatives have been prepared as single olefin isomers through parallel reaction sequences. The products were assayed against multiple enzymes as well as in cell culture studies and surprisingly a Z-olefin isomer was found to be a potent and selective inhibitor of geranylgeranyl diphosphate synthase.

This paper presents an overview of several advanced digital signal processing (DSP)enabled technologies recently demonstrated for high spectral efficiency (SE) 400Gb/s-class transmission, including the SE-adaptable time-domain hybrid QAM, transmitter-side digital spectral shaping, and training-assisted carrier phase recovery.