Role of graphene and transition metal dichalcogenides as hole transport layer and counter electrode in solar cells

Photovoltaic (PV) technology got much attention in the past few decades in developing advanced and environment friendly solar cells (SCs). However, high cost, unstable nature, and low efficiency are major limitations towards commercialization of SCs. To overcome the issues, two-dimensional materials (2DMs) have been exploited due to low cost, high catalytic activity, fast charge separation, and better electrochemical performance. The review emphasis on (a) the electrochemical performance of graphene and transition metal dichalcogenides (TMDCs) as a hole transport layer (HTL) in SCs and (b) to explore low-cost and effective counter electrode (CE) based on graphene and TMDCs for dye-sensitized solar cell (DSSC). The review presents a comparative analysis of 2DMs as HTL and CE to attain highly efficient and low-cost PV devices. Multiple combinations of the material with graphene, graphene oxide (GO), reduced graphene oxide (rGO), tungsten disulfide (WS₂), molybdenum disulfide (MoS₂) as HTL, and CE material in PV cells are discussed and comparatively analyzed. Numerous strategies are briefly discussed to enhance the efficiency of SCs by utilizing graphene and TMDCs based HTL and CEs. The review focuses on the recent progress in developing low-cost and highly efficient PV devices by using 2DMs. Our study reveals that GO/PEDOT:PSS demonstrate a maximum power conversion efficiency (PCE) of 13.1% when fabricated at different revolutions. Moreover, our statistical analysis unveils that efficiency of the cell can be enhanced by optimizing the layer thickness, which provide a route to develop highly efficient and better performance SCs that can be exploited for future commercial applications.     

Dynamic model of a novel thermogravity rotary actuator for solar energy harvesting

The direct conversion of thermal energy to mechanical energy is always been a challenging but demanding problem. In this article, we presented a nonconventional direct conversion mechanism of the readily available solar thermal and gravity energy to rotational mechanical energy. The developed rotating assembly affixed concentrically with a plurality of actuating arms harnesses the integrated solar-gravity energy. Each actuating arm shifts the center of gravity of the attached solid mass with concentrated solar heating. The alternate shift in the center of gravity of each actuating arm with exposure to solar radiation produces a continuous revolution of rotating assembly around its axis of rotation. With a particular set of the system parameters with Al/Si₃N₄ bimetallic strip the thermal efficiency of the proposed thermogravity bimetallic strip heat actuator/engine is 12.41% which is 100 times more efficient compared to a gravity-less thermal engine with same set up. The proposed thermogravity system can generate mechanical power ranges from less than 1 W to 40 kW with a particular set of system parameters. This solar-gravity rotary actuator is a novel work in this domain which has a huge impact and contribution in the available rotary actuator or energy harvester knowledge.     

Synthesis of NiO/Si Using Sol-Gel as a Photosensor

Silicon - Recent studies have indicated that that the application of nickel oxide (NiO) regulator nano-films is growing. The sol-gel method has become the primary method for preparing NiO thin...     

Breathable,Flexible, Transparent,Hydrophobic, and Biotic Sustainable Electrodes for Heating and Biopotential Signal Measurement Applications

Pressure to reduce the global amount of e-waste has increased in recent years. The optimal use of natural resources is a demanding area especially due to the overabundance of the use of resources and challenges with after-life disposal. Herein, an easy method is developed to fabricate an improved version of leaf skeleton-based biodegradable, transparent, flexible, and hydrophobic electrodes. A fractal-like rubber leaf skeleton is used as the substrate, physical vapor deposited Au interlayer to promote adhesion, and uniform deposition of overlayer silver nanowires. The fabricated surfaces present a high level of electrical stability, optical transparency, hydrophobicity, and robust mechanical properties. The prepared electrodes demonstrate a comparable level of optical transmittance to the virgin leaf skeleton. The mechanical sturdiness of the electrodes is verified by 1k bending cycles. To demonstrate the functionality of these hybrid biotic conductive network (HBCN) electrodes, their performance is evaluated as flexible transparent heating elements and as biosignal measurement electrodes. The heater can reach a temperature of 140 °C with only 2.5 V in ≈5 s and Ag nanowire loading of ≈160 μg cm⁻². Likewise, electrocardiogram (ECG) and electromyogram (EMG) signals are successfully obtained from the electrodes without using any electrode gel or other electrolytes.     

A numerical investigation on the performance improvement of axial-flow automotive cooling fan with beads

Journal of Mechanical Science and Technology - This paper presents a CFD analysis of three types of axial-flow magnesium-based automotive cooling fans. The numerical modeling was conducted for...     

Effect of baseline oxygenation on the ventilatory response to inhaled 100% oxygen in preterm infants

We tested the hypothesis that the immediate (< 1 min) ventilatory response to 100% O2 in preterm infants, a test of peripheral chemoreceptor activity characterized by a decrease in ventilation due to apnea, is more pronounced at lower baseline O2 concentrations. We studied 12 healthy preterm infants [birth weight 1,425 +/- 103 (SE) g; study weight 1,670 +/- 93 g; gestational age 30 +/- 1 wk; postnatal age 27 +/- 7 days] during quiet sleep. The infants inhaled 15, 21, 25, 30, 35, 40, and 45% O2 for 5 min in a randomized manner (control period), followed by 100% O2 for 2 min, and then the same initial O2 concentration again for 2 min (recovery period). A nose piece and a flow-through system were used to measure ventilation. The immediate decrease in ventilation with 100% O2 was 46% on 15% O2, 24% on 21% O2, 11% on 25% O2, 8% on 30% O2, 12% on 35% O2, and 8% on 40% O2; there was no decrease on 45% O2 (P < 0.01). The corresponding mean duration of apnea was 29 s during 15% O2, 18 s during 21% O2, 8 s during 25% O2, 9 s during 30 and 35% O2, and 3 s during 40% O2; only one infant developed a 5-s apnea during 45% O2 (P < 0.001). The findings suggest that 1) the ventilatory decrease in response to 100% O2 is dependent on the baseline oxygenation, being more pronounced the lower the baseline O2 concentration; and 2) this ventilatory decrease is entirely related to more prolonged apneas observed with lower baseline O2 concentrations. We speculate that the peripheral chemoreceptors, being so active in the small preterm infant with relatively low arterial PO2, are highly susceptible to changes in PO2, and this makes them prone to irregular or periodic breathing, especially during sleep.     

Low baseline oxygenation predisposes preterm infants to mixed apneas during inhalation of 100% oxygen

We have shown previously that administration of 100% O2 to preterm infants induces an apnea which in about 20% of cases has an obstructive component. The obstruction occurred during the longer apneas. In the present study, we tested the hypothesis that the appearance of obstruction in longer apneas depends on the baseline oxygenation. Sixteen preterm infants were studied in quiet sleep (birthweight 1435 +/- 93 g [mean +/- SEM], study weight 1711 +/- 90 g, gestational age 30 +/- 1 weeks, and postnatal age 26 +/- 5 days) at various baseline oxygenations. A flow-through system was used to measure ventilation and alveolar gases. Respiratory efforts in the absence of flow were detected using chest and abdominal displacements or diaphragmatic electromyography. Each infant inhaled 15%, 21%, or 25% O2 for 5 minutes (control period) followed by 100% O, for 2 minutes. Baseline alveolar PO2, O2 saturation and transcutaneous PO2 increased during inhalation of 15%, 21%, and 25% O2, respectively. The immediate decrease in ventilation with 100% O2 was 52% on 15% O2, 20% on 21% O2, and 16% on 25% O2 (p < 0.001); this was associated with an apnea in all cases. The mean length of apneas during 100% O2 was 37 seconds on 15% O2, 19 seconds on 21%, and 11 seconds on 25% (p < 0.01). Twelve infants (75%) developed mixed obstructive apneas in response to 100% O2 when breathing 15% O2 during control period, three (19%) when breathing 21% O2, and none had mixed apnea when breathing 25% O2 during control period (p < 0.05). These findings suggest that lower baseline oxygenation predisposes to long mixed apneas. We speculate that the peripheral chemoreceptors, uniquely active in the small preterm infant with relatively low O2 tension, when suppressed by an increase in oxygen tension, trigger a central inhibition with loss of upper airway muscle tone. This is more pronounced when the baseline oxygen tension is lower, leading to more prolonged apnea and increased probability of obstruction.     

Effect of temperature on fatty acid composition in the Nile tilapia (Oreochromis niloticus): A temperature dependent nutritive lipid profile

In this study, the effects of temperature on the fatty acids profile and the effects of temperature on the degree of unsaturation of fatty acids of Oreochromis niloticus were investigated. The analysis was performed by gas chromatography. The study showed that there were large temperature variations (10.0–32.0°C) during the study period (January–December). The highest crude fat content was found in January (3380 mg/100 g) and the lowest in June (2050 mg/100 g). The fatty acids profile showed significantly different diversity (p < 0.05). Total saturated fatty acid (∑SFA) content ranged from 409.54 to 1297.61 mg/100 g, monounsaturated fatty acid (∑MUFA) from 207.68 to 665.81 mg/100 g, and polyunsaturated fatty acid (∑PUFA) from 175.12 to 972.23 mg/100 g. The ∑MUFA and ∑PUFA concentrations were highest in January and lowest in June, and the ∑SFA concentration was lowest in January and highest in June. EPA and DHA contents were highest in January (198.96 mg/100 g) and lowest in June (48.76 mg/100 g). The contents of omega-3 (653.17 mg/100 g) and omega-6 fatty acids (252.54 mg/100 g) were highest in January and lowest in June (ω-3; 106.43 and ω-6; 60.91 mg/100 g). It concluded that the degree of unsaturation of fatty acids increases with decreasing temperature. In this study, the nutritional quality of the FAs profile was assessed using lipid quality indices. The indices indicating dietary quality of lipids by their values: Atherogenic index (0.47), thrombogenic index (0.38), hypocholesterolemic to hypercholesterolemic (3.00), meat fat quality (6.78), ω6/ω3 ratio (0.39), PUFA/SFA (2.37), MUFA/SFA (1.62), PUFA/MUFA (1.46), and PUFA + MUFA/SFA (3.99). These values are within the recommended range, indicating that the lipid profile of O. niloticus has high nutritional quality, which can be further improved by harvesting the fish during the winter season. Due to the nutritional importance of O. niloticus, the culture of this species could have significant interest to the people of Karachi, especially the coastal communities. To promote the nutritional diet in local population, the government should support the aquaculture of Nile tilapia.     

盾构刀盘结构设计与分析

盾构是目前土质或以土质为主隧道(洞)工程施工的优选装备,其刀盘结构是实现掌子面稳定、进行隧洞开挖掘进的关键部件.目前盾构刀盘结构主要是辐条式、辐板式和辐条辐板复合结构;大中型盾构刀盘一般采用中间支承形式;为方便刀具更换作业,大型盾构机刀盘已设计出常压刀具更换臂(辐条).此文还对刀盘上刀具布置的刀间距、布置形式等进行了总...