Bidirectional and reversible tuning of the interlayer spacing of two-dimensional materials

Interlayer spacing is expected to influence the properties of multilayer two-dimensional (2D) materials. However, the ability to non-destructively regulate the interlayer spacing bidirectionally and reversibly is challenging. Here we report the preparation of 2D materials with tunable interlayer spacing by introducing active sites (Ce ions) in 2D materials to capture and immobilize Pt single atoms. The strong chemical interaction between active sites and Pt atoms contributes to the intercalation behavior of Pt atoms in the interlayer of 2D materials and further promotes the formation of chemical bonding between Pt atom and host materials. Taking cerium-embedded molybdenum disulfide (MoS2) as an example, intercalation of Pt atoms enables interlayer distance tuning via an electrochemical protocol, leading to interlayer spacing reversible and linear compression and expansion from 6.546 ± 0.039 Å to 5.792 ± 0.038 Å (~11 %). The electronic property evolution with the interlayer spacing variation is demonstrated by the photoluminescence (PL) spectra, delivering that the well-defined barrier between the multilayer and monolayer layered materials can be artificially designed.

Effect of High Pressure and Temperature on the Evolution of Si Phase and Eutectic Spacing in Al-20Si Alloys

The microstructure of the Si phase in Al-20Si alloys solidified under high pressure was investigated. The results demonstrate that the morphology of Si phase transformed (bulk→short rod→long needle) with the increase of superheat temperature under high pressure. At a pressure of 3 GPa and a superheat temperature of 100 K, a microstructure with a uniform distribution of fine Si phases on the α-Al matrix was obtained in the Al-20Si alloy. In addition, a mathematical model was developed to analyze the spacing variation of the lamellar Al-Si eutectics under the effect of pressure. The lamellar Al-Si eutectics appeared at 2 GPa and superheat temperatures of 70–150 K, and at 3 GPa and superheat temperatures of 140–200 K. With the increase of pressure from 2 GPa to 3 GPa, the average spacing of lamellar Al-Si eutectics decreased from 1.2–1.6 μm to 0.9–1.1 μm. In binary alloys, the effect of pressure on the eutectic spacing is related to the volume change of the solute phase from liquid to solid. When the volume change of the solute phase from liquid to solid is negative, the lamellar eutectic spacing decreases with increasing pressure. When it is positive, the eutectic spacing increases with increasing pressure.

Clustering Algorithm Based Straight and Curved Crop Row Detection Using Color Based Segmentation

Autonomous navigation of agricultural robot is an essential task in precision agriculture, and success of this task critically depends on accurate detection of crop rows using computer vision methodologies. This is a challenging task due to substantial natural variations in crop row images due to various factors, including, missing crops in parts of a row, high and irregular weed growth between rows, different crop growth stages, different inter-crop spacing, variation in weather condition, and lighting. The processing time of the detection algorithm also needs to be small so that the desired number of image frames from continuous video can be processed in real-time. To cope with all the above mentioned requirements, we propose a crop row detection algorithm consisting of the following three linked stages: (1) color based segmentation for differentiating crop and weed from background, (2) differentiating crop and weed pixels using clustering algorithm and (3) robust line fitting to detect crop rows. We test the proposed algorithm over a wide variety of scenarios and compare its performance against four different types of existing strategies for crop row detection. Experimental results show that the proposed algorithm perform better than the competing algorithms with reasonable accuracy. We also perform additional experiment to test the robustness of the proposed algorithm over different values of the tuning parameters and over different clustering methods, such as, KMeans, MeanShift, Agglomerative, and HDBSCAN.

Thermal-Hydraulic Performance Enhancement by the Combination of Rectangular Winglet Pair and V-Shaped Dimples

This paper presents numerical study on heat transfer enhancement due to the combination of rectangular winglet pair with V-dimples in an array-type arrangement. Array of rectangular winglet pairs results in heat transfer enhancement, however, at a cost of significant pressure drop, resulting in reduced thermal-hydraulic performance (THP). On the other hand, dimples are associated with lower heat transfer enhancement levels at relatively lower pumping power penalty. To this end, a combination of rectangular winglet pair and V-shaped dimples has been studied in this paper, where the arrangements were intended to achieve enhanced thermal-hydraulic performance. Three different configurations, namely, rectangular winglet pair, rectangular winglet pair with one V-dimple between two consecutive winglets, and rectangular winglet pair with two V-dimples packed in a pitch, are studied here. The variation of heat transfer enhancement, pressure drop gain, and THP with respect to winglet-to-winglet (S) spacing variation for rectangular winglet pair and rectangular winglet pair with one V-dimple configuration is presented at a Reynolds number of 25,000. The THP of the rectangular winglet pair configuration decreases up to S/H equal to 2.5 and then increases (H: channel height). For rectangular winglet pair with one V-dimple, three values of winglet-to-dimple (P) spacings are analyzed. For fixed S/H, the highest P/H configuration provided highest heat transfer enhancement and THP. Among the three configurations studied, rectangular winglet pair with two V-dimples resulted in the highest thermal-hydraulic performance.

Numerical Study on Aero-Hydrodynamics With Inter-Turbine Spacing Variation for Two Floating Offshore Wind Turbines

To investigate the influence of the inter-turbine spacing on the performance of the floating offshore wind turbine (FOWT) in the floating wind farm, coupled aero-hydrodynamic simulations of two spar-type FOWT models with inter-turbine spacing variation under shear wind and regular wave conditions are performed in the present work. An unsteady actuator line model (UALM) is embedded into in-house code naoe-FOAM-SJTU to establish a fully coupled CFD analysis tool for numerical simulations of FOWTs. From the simulation results, the unsteady aerodynamic power and thrust are obtained, and the hydrodynamic responses including the six-degree-of-freedom motions and mooring tensions are available. Detailed flow visualizations of wake velocity profiles and vortex structures are also illustrated. The coupled performance of floating offshore wind turbines with inter-turbine spacing variation are analyzed, and the influences of inter-turbine spacing on aero-hydrodynamic characteristics of coupled wind-wave flow field are discussed. It is found that the power output of downstream wind turbine increases with inter-turbine spacing. Coupled aero-hydrodynamic characteristics of flow filed are significantly affected by inter-turbine spacing.

A Novel Method for the Micro-Clearance Measurement of a Precision Spherical Joint Based on a Spherical Differential Capacitive Sensor

A spherical joint is a commonly used mechanical hinge with the advantages of compact structure and good flexibility, and it becomes a key component in many types of equipment, such as parallel mechanisms, industrial robots, and automobiles. Real-time detection of a precision spherical joint clearance is of great significance in analyzing the motion errors of mechanical systems and improving the transmission accuracy. This paper presents a novel method for the micro-clearance measurement with a spherical differential capacitive sensor (SDCS). First, the structure and layout of the spherical capacitive plates were designed according to the measuring principle of capacitive sensors with spacing variation. Then, the mathematical model for the spatial eccentric displacements of the ball and the differential capacitance was established. In addition, equipotential guard rings were used to attenuate the fringe effect on the measurement accuracy. Finally, a simulation with Ansoft Maxwell software was carried out to calculate the capacitance values of the spherical capacitors at different eccentric displacements. Simulation results indicated that the proposed method based on SDCS was feasible and effective for the micro-clearance measurement of the precision spherical joints with small eccentricity.

Perbedaan kualitas dan vase life bunga krisan akibat aplikasi macam pupuk organik dengan variasi jarak tanam

Chrysantemum much appreciated by the public for its beautiful colors and shapes, and has a longer vase life. Quality and vase life of chrysanthemum flowers not only was influenced by post harvest conditions but also the management during plant growth. Light, temperature, relative humidity, fertilization and spacing arrangement on cultivated plant are factors that can affect the quality and vase life of flowers. An experiment was conducted to study the variation of organic fertilizer application effect on quality and vase life of Chrysan-themum flowers with different row spacing, and to find out of organic fertilizer and row spacing which gave the best quality and vase life of Chrysanthemum flowers. Experimental design was used Split Plot Design with two factors: kinds of organic fertilizer as main plot and su plot was row spacing. Kinds of organic fertilizers consisted four levels: chicken, sheep, rabbit and cow dung, and three levels of row spacing : 10 cm x 10 cm, 15 cm x 10 cm and 20 cm x 10 cm. Those treatment combinations were repeated three times. Result of this experiment showed that application of organic fertilizer affected for the quality of chrysanthemum flowers in row spacing variation. Rabbit or sheep dung of organic fertilizer application gave the best of flower stalk and diameter of flowers, flowers of grade I > 60%, and vase life more than 13 days, if was planted with 20 cm x 10 cm row spacing.Keywords: Chrysanthemum, Kinds of organic fertilizer, Row spacing, Quality and vase lifeSari. Krisan banyak disukai masyarakat karena keindahan bentuk dan warna serta memiliki vase life yang lebih lama. Kualitas dan vase life bunga krisan tdak hanya dipengaruhi oleh kondisi pascapanen, tetapi juga dipengaruhi oleh management selama pertumbuhan tana-man. Cahaya, temperatur, kelembaban, pemu-pukan dan pengaturan jarak tanam dalam teknik budidaya merupakan faktor-faktor yang dapat mempengaruhi kualitas dan vase life bunga krisan. Suatu percobaan bertujuan untuk mempelajari efek aplikasi macam pupuk organik terhadap kualitas dan vase life bunga krisan pada variasi jarak tanam dan mendapat-kan macam pupuk organik dan jarak tanam yang memberikan kualitas dan vase life bunga krisan yang terbaik. Percobaan menggunakan Rancangan Petak Terbagi dengan dua faktor perlakuan, yaitu macam pupuk organik sebagai petak utama dan jarak tanam sebagai anak petak. Macam pupuk organik terdiri atas empat taraf : pupuk kandang ayam, sapi, domba dan kelinci yang diberikan dengan dosis 30 t ha-1 dan diaplikasikan pada saat tanam. Jarak tanam terdiri atas tiga taraf: 10 cm x 10 cm, 15 cm x 10 cm, dan 20 cm x 10 cm. Kombinasi kedua taraf factor perlakuan diulang sebanyak tiga kali. Hasil percobaan menunjukkan bahwa aplikasi macam pupuk organik berpengaruh terhadap kualitas bunga dan vase life pada variasi jarak tanam. Aplikasi pupuk organik kelinci atau domba dengan penanaman berjarak 20 cm x 10 cm memberikan panjang tangkai bunga dan diameter bunga terbaik, persentase bunga kelas I di atas 60% serta vase life lebih dari 13 hari.Kata kunci: Jarak tanam, Macam pupuk organik, Kualitas dan Vase life, Krisan

Analysis of Microwaviness-Excited Vibrations of a Flying Head Slider in Proximity and Asperity Contact Regimes

The vibration characteristics of a thermal fly-height control (TFC) head slider in the proximity and asperity contact regimes attract much attention, because the head–disk spacing (HDS) must be less than 1 nm in order to increase the recording density in hard disk drives. This paper presents a numerical analysis of the microwaviness (MW)-excited vibrations in the flying head slider during the touchdown (TD) process. We first formulate the total force applied to the TFC head slider as a function of the HDS, based on rough-surface adhesion contact models and an air-bearing force model. Then, the MW-excited vibrations of a single-degree-of-freedom (DOF) slider model at TD are simulated by the Runge–Kutta method. It is found that, when the MW amplitude is less than the spacing range of static instability in the total force, the slider jumps to a contact state from a near-contact or mobile-lubricant-contact state. It then jumps to a flying state even when the head surface is protruded further by increasing the TFC power. When the MW amplitude is relatively large, a drastically large spacing variation that contains a wide range of frequency components below 100 kHz appears in the static unstable region. These calculated results can clarify the mechanisms behind a few peculiar experimental phenomena reported in the past.