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排序方式： 共有1712条查询结果，搜索用时 9 毫秒
71.
Syed Ajijur Rahman Himlal Baral Roshan Sharma Yusuf B. Samsudin Maximilian Meyer Michaela Lo Yustina Artati Trifosa Iin Simamora Sarah Andini Budi Leksono James M. Roshetko Soo Min Lee Terry Sunderland 《Food and Energy Security》2019,8(3)
Growing bioenergy crops on degraded and underutilized land is a promising solution to meet the requirement for energy security, food security, and land restoration. This paper assesses the socioeconomic and environmental benefits of agroforestry systems based on nyamplung (tamanu) (Calophyllum inophyllum L.) in the Wonogiri district of Central Java, Indonesia. Data were collected through field observations and focus group discussions involving 20 farmers who intercrop nyamplung with maize, rice, and peanuts and utilize the species in honey production. Calculating each crop's net present value (NPV) demonstrates that when grown as monocultures, staple crops rice and peanuts lead to negative profitability, while maize generates only a marginal profit; yet honey production utilizing nyamplung produces a NPV nearly 300 times greater than maize. However, when utilizing nyamplung, honey is also the commodity most sensitive to decreases in production, followed by nyamplung–peanut and nyamplung–rice combinations. While decreases in production have little effect on the NPVs of rice, peanuts, and maize, these annual crops can only be cultivated for a maximum of 6 years within the nyamplung's 35‐year cycle, due to canopy closure after this time. Nyamplung‐based agroforestry systems can provide economic, social, and environmental gains on different scales. However, when considering the high profit potential of nyamplung combined with honey production, further research is needed to improve and develop bee husbandry practices so this becomes a viable option for local farmers. 相似文献
72.
Syed N. Shah Mushtaq Ahmad Muhammad Zafar Fazal Ullah Wajid Zaman Khafsa Malik Neelam Rashid Saba Gul 《Microscopy research and technique》2019,82(8):1326-1333
Spore morphology of Thelypteridaceae species growing in Malakand Division, Northern Pakistan, was studied using both light microscopy and scanning electron microscopy. The taxa are Christella dentata and Glaphyropteridopsis erubescens in the subfamily Thelypteridoideae, and Phegopteris connectilis, Pseudophegopteris pyrrhorhachis, and Pseudophegopteris levingei in the subfamily Phegopteridoideae. The studied species exhibit differences in spore size, exospore thickness, color, and ornamentation. Spores of the studied species are monolete and medium‐sized, and shape is ellipsoidal in both polar and equatorial views. The average measurement of the polar diameter ranges from 27 μm to 31 μm, whereas in the equatorial direction it varied from 20 μm to 40 μm. The exospore thickness ranges from 1.2 μm to 2.4 μm. Reticulate, laevigate with microgranules, cristate, and coarsely echinate surface ornamentation are observed among the species. Multivariate analysis including unweighted pair group method with arithmetic mean and principal component analysis was used for the grouping and discrimination of species and genera. 相似文献
73.
Rajender Prasad Tiwari Syed Zimad Husain Hashmi Raghav Sharma Saif Ahmad Khan Balaji Birajdar 《Journal of the American Ceramic Society》2019,102(8):4659-4669
Residual NiO phase is generally detected in 0.9(KNbO3)–0.1(BaNi1/2Nb1/2O3-δ) (KBNNO) synthesized using NiO as a nickel precursor by solid-state reaction. In this work, NiO phase is found to exist in the form of the residual NiO particles with a size of 100-200 nm using energy dispersive X-ray elemental mapping. These NiO residual particles are eliminated by using nickel acetate as a nickel precursor and a 100% perovskite phase KBNNO is successfully synthesized at as low as 600°C temperature. Furthermore, using the two-step sintering technique, 100% relative density is achieved in this material. The nickel acetate–based KBNNO shows a robust ferromagnetism with the saturation magnetization of 11.42 memu/g and the remanent magnetization of 3.89 memu/g which is 38 times higher than that of previously reported value in NiO-based KBNNO. Thus, a highly pure and fully dense KBNNO ceramic with superior magnetic properties is obtained using nickel acetate and by the two-step sintering method. This is a key step forward in the processing of KBNNO and is likely to have a significant impact on other physical properties of this newly invented and promising photovoltaic perovskite material. 相似文献
74.
Raasti Naseem Liguo Zhao Vadim V. Silberschmidt Yang Liu Senthil K. Eswaran Syed Hossainy 《Polymer Engineering and Science》2019,59(5):1084-1091
Measurement of mechanical parameters of polymeric scaffolds presents a significant challenge due to their intricate shape and small characteristics dimensions of their elements—around 100 μm. In this study, mechanical properties of polymeric tubing and scaffold, made of biodegradable poly(l ‐lactic) acid (PLLA), were characterized using atomic force microscopy (AFM) and nanoindentation, complemented with tensile testing. AFM was employed to assess the properties of the tube and scaffold locally, while nanoindentation produced results with a dependency on the depth of indentation. As a result, the AFM‐measured elastic modulus differs from the nanoindentation data due to a substantial difference in indentation depth between the two methods. With AFM, a modulus between 2 and 2.5 GPa was measured, while a wide range was obtained from nanoindentation on both the tube and scaffold, depending on the indentation scale. Changes in the elastic modulus with in‐vitro degradation and aging were observed over the 1‐year period. To complement the indentation measurements, tensile testing was used to study the structural behavior of the tube, demonstrating the yielding, hardening and fracture properties of the material. POLYM. ENG. SCI., 59:1084–1091, 2019. © 2019 Society of Plastics Engineers 相似文献
75.
Syed Alay Hashim Pawan Kumar Ojha Srinibas Karmakar Arnab Roy Debasis Chaira 《Propellants, Explosives, Pyrotechnics》2019,44(7):896-907
An extensive diversity in the formulation of HTPB‐based solid fuels with metal additives has now been accepted in rocket and missile applications. Boron, which is a metalloid and often occurs in compound form has maintained its dominance mainly due to its significant theoretical energy potential. Therefore, it is preferred as the primary choice for rockets and solid fuel ramjet (SFRJ) or ducted rocket (SFDR). In this paper, performance enhancement of B−HTPB‐based solid fuel is assessed through a rapid screening tool which is called an opposed flow burner (OFB). Screened fuel combinations may be further evaluated in the gas generator of a ducted rocket (DR) to fulfill the intention of the present investigation. The baseline fuel (B−HTPB) is included with a metal fuel/catalyst (iron) with the expectation that it would enhance the combustion performance of boron. Boron−iron loading has been taken 10 % of the total sample weight (wt.) giving a wt. ratio of 90 : 10. Pure oxygen has been used as an oxidizer which impinges on the fuel surface where oxygen mass flux (Gox) varies between 20–57 kg/m2‐s. In this study, the research focuses mainly on regression rate and amount of residual active boron in the condensed combustion product (CCP) of the samples. Addition of iron to B−HTPB increases the regression rate by around 12 % and active boron content in CCP reduces significantly to 2.5 % compared to 16 % of the baseline fuel. In addition to that, the heating value of the fuel samples and identification of gas phase intermediate species (OH, CH, C2, BO, BO2) are the other vital investigations undertaken in the present study. 相似文献
76.
Sandhya Susarla Praveena Manimunda Ygor M. Jaques Jordan A. Hachtel Juan C. Idrobo S. A. Syed Asif Douglas S. Galvo Chandra Sekhar Tiwary Pulickel M. Ajayan 《Advanced Materials Interfaces》2019,6(5)
The possibility of tuning properties and its potential applications in the fields of optoelectronics and/or flexible electronics, has increased the demand for 2D alloys in recent times. Understanding the mechanical performance of 2D materials under extreme conditions, such as strain, stress, and fracture is essential for the reliable electronic devices based on these structures. In this study, combined molecular dynamics (MD) simulations and in situ Raman spectroscopic techniques are used to study the mechanical performance of a 2D alloy system, MoxW(1‐x) S2. It is observed that W substitution in MoS2 causes solid‐solution strengthening and increase in the Young's modulus values. Higher W content decreases failure strain for MoS2. Based on spatially resolved Raman spectroscopy and MD simulations results, a detailed model to explain failure mechanisms in MoxW(1‐x) S2 alloys is proposed. 相似文献
77.
Syed Atif Pervez Pejman Ganjeh‐Anzabi Umer Farooq Milana Trifkovic Edward P. L. Roberts Venkataraman Thangadurai 《Advanced Materials Interfaces》2019,6(11)
While all‐solid‐state Li metal batteries based on ceramic solid‐electrolytes offer higher energy density and better safety features over their liquid counterparts, critical challenges in their design such as high electrode–electrolyte interface resistance and formation of Li‐dendrites still remain unsolved. To address the issues, an intimate contact between Li and the solid‐state electrolyte is necessary. Herein, a flexible and mechanically robust polymer membrane comprising of poly(ethylene oxide), lithium perchlorate, and garnet particles is used as an interlayer between Li metal and garnet ceramic electrolyte. The Li salt enhances the ionic conductivity of the membranes and ensures their flexible nature while garnet particles enhance their mechanical strength. The cells comprising of composite membranes results in four times smaller charge transfer resistance at the interface and demonstrate stable and reversible Li plating/stripping voltage profiles. Further, the polymer composite membrane mechanically blocks the formation of Li dendrites at reasonably high currents (0.1 mA cm−2) in the structures even after prolonged cycling (140 h) owing to their enhanced toughness. With smaller charge transfer resistance (≈400 Ω cm2 at room temperature), stability at extended periods of cycling and no Li‐dendrite formations, the structures can prove a viable electrolyte candidate for advanced solid‐state Li metal batteries. 相似文献
78.
The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES. 相似文献
79.
Syed Adeel Ali Shah Ejaz Ahmed Muhammad Ahsan Qureshi Sadeeq Jan Rafidah MD Noor 《International Journal of Communication Systems》2019,32(13)
In safety‐critical scenarios, reliable reception of beacons transmitted by a subject vehicle is critical to avoid vehicle collision. According to the employed contention window sizes in IEEE 802.11p, beacons are transmitted with a small contention window size. As a result, multiple vehicles contend for the shared channel access by selecting the same back‐off slot. This is a perfect recipe for synchronous collisions wherein reliable beacon delivery cannot be guaranteed for any vehicle. We consider the problem of selecting the back‐off slots from the current contention window to provide reliable delivery of beacons transmitted by a subject vehicle to its neighbors. Given a safety scenario, we propose a Pseudo‐Random Number Generator (PRNG)‐inspired back‐off selection (PBS) technique. The proposed technique works on the hypothesis that synchronous collisions of beacons transmitted by a subject vehicle can be reduced if all its neighbors select different back‐off slots (ie, not the back‐off slot selected by the subject vehicle). The discrete‐event simulations demonstrate that PBS can increase the overall message reception from a subject vehicle, in comparison with the uniform random probability back‐off selection in IEEE 802.11p. 相似文献
80.