Effectiveness of Africa's tropical protected areas for maintaining forest cover

The effectiveness of parks for forest conservation is widely debated in Africa, where increasing human pressure, insufficient funding, and lack of management capacity frequently place significant demands on forests. Tropical forests house a substantial portion of the world's remaining biodiversity and are heavily affected by anthropogenic activity. We analyzed park effectiveness at the individual (224 parks) and national (23 countries) level across Africa by comparing the extent of forest loss (as a proxy for deforestation) inside parks to matched unprotected control sites. Although significant geographical variation existed among parks, the majority of African parks had significantly less forest loss within their boundaries (e.g., Mahale Park had 34 times less forest loss within its boundary) than control sites. Accessibility was a significant driver of forest loss. Relatively inaccessible areas had a higher probability (odds ratio >1, p < 0.001) of forest loss but only in ineffective parks, and relatively accessible areas had a higher probability of forest loss but only in effective parks. Smaller parks less effectively prevented forest loss inside park boundaries than larger parks (T = ?2.32, p < 0.05), and older parks less effectively prevented forest loss inside park boundaries than younger parks (F_2,154 = ?4.11, p < 0.001). Our analyses, the first individual and national assessment of park effectiveness across Africa, demonstrated the complexity of factors (such as geographical variation, accessibility, and park size and age) influencing the ability of a park to curb forest loss within its boundaries.     

Modelling and Prediction of Diesel Engine Performance using Relevance Vector Machine

Diesel engines are being increasingly adopted by many car manufacturers today, yet no exact mathematical diesel engine model exists due to its highly nonlinear nature. In the current literature, black-box identification has been widely used for diesel engine modelling and many artificial neural network (ANN) based models have been developed. However, ANN has many drawbacks such as multiple local minima, user burden on selection of optimal network structure, large training data size, and over-fitting risk. To overcome these drawbacks, this article proposes to apply an emerging machine learning technique, relevance vector machine (RVM), to model and predict the diesel engine performance. The property of global optimal solution of RVM allows the model to be trained using only a few experimental data sets. In this study, the inputs of the model are engine speed, load, and cooling water temperature, while the output parameters are the brake-specific fuel consumption and the amount of exhaust emissions like nitrogen oxides and carbon dioxide. Experimental results show that the model accuracy is satisfactory even the training data is scarce. Moreover, the model accuracy is compared with that using typical ANN. Evaluation results also show that RVM is superior to typical ANN approach.     

Investigation of Nanoparticle Additives to Biodiesel for Improvement of the Performance and Exhaust Emissions in a Compression Ignition Engine

Worldwide energy demand has been growing steadily during the past five decades and most experts believe that this trend will continue to rise. The amount of emitted harmful emission gases increases in parallel with increasing energy consumption. This increase has forced many countries to take various precautions, and various restrictions on emitted emissions have been carried. In this study, effects of addition of oxygen containing nanoparticle additives to biodiesel on fuel properties and effects on diesel engine performance and exhaust emissions were investigated. Two different nanoparticle additives, namely MgO and SiO₂, were added to biodiesel at the addition dosage of 25 and 50 ppm. Fuel properties, engine performance, and exhaust emission characteristics of obtained modified fuels were examined. As a result of this study, engine emission values NO_x and CO were decreased and engine performance values slightly increased with the addition of nanoparticle additives.     

Experimental study on fire suppression performance of the high pressure water mist in the engine room of an offshore platform

The total flooding application water mist system is a new type of environmentally-friendly fixed extinguishing system. The optimizing design can improve its fire extinguishing performance. At present, the water mist fire extinguishing system in the engine room of the offshore deepwater semi-submersible support platform has not attracted sufficient attention. In this paper, the water mist in the engine room of a deepwater semi-submersible support platform was studied. It contains the effect of water mist on the heat absorption and oxygen insulation of diesel pool fires. The applicable parameters of the water mist fire extinguishing system were also determined. Moreover, based on the shielding of the fire source in the engine room and the different requirements for water mist extinguishing parameters, a hierarchical multi-parameter combined high-pressure water mist fire extinguishing system was proposed. In the full-scale experimental engine room model, according to the fire extinguishing experiments for diesel pool fires with different areas, this kind of hierarchical multi-parameter water mist system is very effective on shielded and non-shielded fires. In addition, it is still effective even in a non-closed environment coupled with smoke exhausting.     

飞机发动机舱灭火剂用量试验验证与优化研究

为提升飞机的安全性,飞机防火系统越来越受到重视。航空防火系统中常用灭火剂Halon 1301会破坏臭氧层、造成环境污染,但至今仍未找到理想的替代品。从优化灭火剂的用量着手,以达到降低污染、减轻飞机重量的目的。目前灭火剂的用量没有结合实际仅依靠理论公式进行计算,为优化灭火剂用量,以某型飞机发动机舱防火系统为例,通过模拟真实环境试验验证不同灭火剂用量下的灭火效果。结果表明优化灭火剂用量后依然能充分地保证灭火效果。     

Age and engine displacement are associated with unsafe motorcycle rider actions

Background: Our goal was to examine the relationship between age and engine displacement in cubic centimeters (CCs) and crash responsibility. Methods: Male motorcyclists, aged 16–94, involved in a fatal crash in the United States (1987–2015) who tested negative for both drugs and alcohol were included. Employing a case control design, cases had committed one or more Unsafe Motorcyclist Actions (UMAs), the proxy measure of responsibility; controls had no UMAs recorded. Odds ratios were computed via multinomial regression examining the effect of motorcyclists’ age and motorcycle displacement (up to 1500 CCs, in 250 CC increments) on crash responsibility by any UMA and top three individual UMAs committed. Results: A total of 19,166 motorcyclists met our inclusion criteria. Increased displacement was observed in older motorcyclists and in more recent crashes. Fifty-six percent of motorcyclists committed one or more UMAs (n = 10,743). The top three individual UMAs were: Speeding (35%, n = 6,728), Weaving (24%, n = 3,269), and Erratic Operation (6%, n = 1,162). Odds ratios for committing any UMA were the greatest for riders on 750 CC motorcycles, followed closely by 500 and 1000 CC motorcycles. By 1250 CCs the effect of displacement on rider crash responsibility (any UMA) was no longer statistically significant. Typically, younger ages (e.g., 20–30) on motorcycles with 500–1000 CCs were associated with the highest odds of either speeding, weaving, or erratic riding compared to similar aged riders on 250 CC motorcycles. Exceptions were observed, for example riders at 70 years of age on 1500 CCs having higher odds of speeding than younger riders on equivalent CC motorcycles. Conclusion: Education and legislative measures should be considered. Educationally, the development of training interventions focusing on control, stability, and breaking differences with more powerful motorcycles (750 to 1250 CCs) is needed. Legislatively, licensing tiers could be employed based on displacement and educational requirements. Education and legislative measures could help to curb the trend seen between high-powered motorcycles and crash responsibility.     

低能耗低成本排气消声器的研制

利用正交设计方法对汽车的排气消声器进行优化设计 ,弄清了不同参数对消声器性能的影响和变化规律。通过正交设计 ,使新消声器的各项指标得到提高。     

汽车公害及其综合防治办法

论述了汽车公害的危害性及减少汽车污染的各种综合防治方法－排气净化，革新燃烧系统及发动机等，并展望未来将采用的低污染代用燃料及低污染发动机或无污染动力源．     

The influence of air–fuel ratio on engine performance and pollutant emission of an SI engine using ethanol–gasoline-blended fuels

Ethanol–gasoline-blended fuel was tested in a conventional engine under various air–fuel equivalence ratios (λ) for its performance and emissions. The amount of fuel injection was adjusted manually by an open-loop control system using a CONSULT controller. It was found that without changing throttle opening and injection strategy, λ could be extended to a leaner condition as ethanol content increased. The results of engine performance tests showed that torque output would increase slightly at small throttle valve opening when ethanol–gasoline-blended fuel was used. It was also shown that CO and HC emissions were reduced with the increase of ethanol content in the blended fuel, which resulted from oxygen enrichment. At an air–fuel equivalence ratio slightly larger than one, the smallest amounts of CO and HC and the largest amounts of CO₂ resulted. It was noted that under the lean combustion condition, CO₂ emission was controlled by air–fuel equivalence ratio; while under the rich combustion condition, CO₂ emission is offset by CO emission. It was also found that CO₂ emission per unit horse power output for blended fuel was similar or less than that for gasoline fuel. From the experimental data, the optimal ethanol content in the gasoline and air–fuel equivalence ratio in terms of engine performance and air pollution was found.     

绿色机动车—燃料电池汽车

简要叙述了燃料电池汽车的技术特点，主要有：能量转化效率高，ＣＯ２排放量比内燃机汽车低，基本不产生有毒气体，不要充电。在此基础上较详细地介绍了世界各国的燃料电池汽车研究现状，并针对上海市机动车污染严重的现状，提出了发展燃料电池汽车及其相关产业的建议。