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Sapindus mukorossi seeds are commonly drilled and processed into Buddha beads and other craft products. To improve the machining qualities of the micro-drilling of S. mukorossi seeds, the effects of drilling parameters (feed rate, drilling speed, and drill diameter) on the drilling force, hole diameter and hole morphology were found. The mechanism behind these changes was further analyzed. The drilling parameters and machining process for the micro-drilling of S. mukorossi seeds were optimized. Results indicated that each drilling parameter influenced the drilling force and hole-machining quality by affecting the amount of cutting, the working conditions of the drill bit, chip formation, and the generation of drilling heat. Moreover, the feed rate and drill diameter were the main factors that influenced the drilling force, and the drilling speed played a leading role that influenced hole-machining quality. Interestingly, for the drilling of S. mukorossi seeds, a feed rate of 0.03 mm/r, a drilling speed of 6 m/min, and a drill-bit diameter of 0.9 or 1.5 mm resulted in a hole with high accuracy, good hole morphology, and minimal wear on the drill bit. This study facilitates the selection of suitable drilling parameters and processing technology for the micro-drilling of S. mukorossi seeds to improve processing accuracies and qualities, and provides a theoretical basis for the improvement of related drilling processing equipment.

Sapindus mukorossi seeds are commonly drilled and processed into strings and other craft products. To improve the machining qualities of micro-drilling of S. mukorossi seeds, the effects of these drilling parameters on the drilling force and pore morphology were found. The mechanism behind these changes was further analyzed. The drilling parameters (feed rate, drilling speed, and drill diameter) and machining process for the micro-drilling of S. mukorossi seeds were optimized. Results indicated that each drilling parameter influenced the drilling force and hole-machining quality by affecting the amount of cutting, the working conditions of the drill bit, chip formation, and the generation of drilling heat. Moreover, the feed rate and drill diameter are main influence factors that influence the drilling force, and the drilling speed plays a leading role that influences the hole-machining quality. Interestingly, for the drilling of S. mukorossi seeds, a feed rate of 0.03 mm/r, a drilling speed of 6 m/min, and a drill-bit diameter of 0.9- or 1.5 mm resulted in a hole with high accuracy, good pore morphology, and minimal wear on the drill bit. This study facilitates the selection of suitable drilling parameters and processing technology for the micro-drilling of S. mukorossi seeds to improve the processing accuracies and qualities, and provides a theoretical basis for the improvement of related drilling processing equipment.

Two-phase closed thermosyphons have good thermal conductivity and are widely used in heat transfer applications. It is essential to establish an effective method for evaluating the steady-state heat transfer performance of two-phase closed thermosyphons, as such a method can help to select appropriate designs and to improve the efficiency of these devices. In this paper, the equivalent thermal conductivity is derived by the principle of equal total thermal resistance, in which the influence of the adiabatic length is eliminated. An evaluation model of the steady-state heat transfer performance of two-phase closed thermosyphons is established. Test results of three two-phase closed thermosyphons with total lengths of 220 mm, 320 mm, and 500 mm show that as the heat transfer rate increases, the equivalent thermal conductivity of these devices decreases by 28.91%, increases by 6.10% and increases by 10.02%, respectively, among which the minimum value is 831.63 W/mK and the maximum value is 1694.19 W/mK. The decrease (in-crease) in the equivalent thermal conductivity in the evaluation model indicates a decrease (increase) in the heat transfer performance. The results show that the equivalent thermal conductivity of the model can effectively evaluate the heat transfer performance of two-phase closed thermosyphons.

The shallow feature map of the single-shot detector (SSD) is not always conducive to enhancing the recognition precision for a small object because of the lack of contextual information. In this research, a single-shot detection algorithm based on cyclic attention (CA-SSD) is proposed to construct a fast and accurate detector that efficiently obtains full-image contextual information. Our network is constructed by integrating ResNet-34 and proposed novel cyclic attention blocks. This type of building block aggregates different transformations, one of which includes an attention module that uses a long but narrow pooling kernel to acquire horizontal and vertical contextual information for each pixel of all pixels. Each pixel eventually captures the full-image dependencies by following an even further cyclic operation. Our design considers the variability of the gradient, which not only improves the reliability of the cyclic attention block but also cuts the number of parameters for computation. Additionally, by exploring the effects of the stem block and its stride on the performance of ResNet-based SSD algorithms, our network retains more detailed information. For an input size of 300 $\times $ 300, CA-SSD attained 82.5% mAP on PASCAL VOC 2007 test, 78.4% mAP on PASCAL VOC 2012 test, and 32.7% mAP on MS COCO. Experimental results achieved with CA-SSD surpass the best results achieved with the traditional SSD and other advanced object detection algorithms while real-time speed is maintained.

This study predicts pyrolytic product yields via machine learning algorithms from biomass physicochemical characteristics and pyrolysis conditions. Random forest (RF), gradient boosting decision tree (GBDT), eXtreme Gradient Boosting (XGBoost), and Adaptive Boost (Adaboost) algorithms are comparatively analyzed. Among these algorithms, the RF algorithm is the best modeling algorithm and performs best in predicting the bio-oil yield and performs well in predicting biochar and pyrolytic gas yields. The moisture content, carbon content, and final heating temperature are the most important factors in predicting pyrolysis product yields, and biomass characteristics are more important than pyrolysis conditions. Furthermore, the carbon content positively affects the bio-oil yield and negatively affects the biochar yield, and the final temperature positively affects the pyrolytic gas yield and negatively affects the biochar yield. This work provides new insight for controlling the yields of pyrolytic products via the RF algorithm, which can facilitate the process optimization in engineering applications.

Accurate understanding of the frictional behavior at the tool-chip interface is critical for the cutting process. To quantitatively analyze the ratio of the sticking contact length to tool-chip contact interface length, a concise calculation model was proposed. Orthogonal cutting experiments and friction experiments were conducted to acquire the friction coefficients for use as input parameters to the model. Calculations found that the ratio, the sliding contact length, and the tool-chip contact interface length showed downward tendencies with increasing cutting speed. The maximum value of the ratio was 63.2 %, achieved at 1000 m/min, whereas the minimum was 58.6 %, achieved at 800 m/min. Furthermore, as the cutting speed rises, the sliding and apparent friction coefficients decrease, while the sticking friction coefficient remains nearly constant. The findings are helpful to improve people’s cognition of sticking-sliding contact, the quality of machining, and determine the thickness and length of the tool coating.

HighlightsAnalyzing the fruit removal force and harvesting time of Sapindus fills a gap of Sapindus research.A dual excitation vibration method for harvesting Sapindus and the best harvesting parameters were obtained.The microstructure of the different fracturing locations was analyzed for the first time. Abstract.To address the issue of labor intensity in the harvest of Sapindus fruit, it is necessary to understand the harvesting properties of Sapindus mukorossi. In this study, a fruit removal force (FRF) test platform was used to analyze the relationship between the FRF and maturation time. An eccentric vibration harvesting test was conducted to obtain the frequency, acceleration, and other parameters of the Sapindus tree. According to the different falling locations of fruit, the fracturing locations were observed by a scanning electron microscope (SEM). The results revealed that the optimal time (9 to 12 November) to harvest is in the middle of the harvest period. Additionally, the shear force from 1.0N to 5.2 N was less than the tensile force from 2.7 to 10.2 N. Therefore, back and forth swinging is the major fracturing form of the fruit. Moreover, dual excitation is preferable to single-point excitation, and the acceleration root mean square (RMS) of the dual excitation was two to three times the acceleration RMS of single point excitation. The harvesting efficiency of dual excitation was 92.3% at 20 Hz. Additionally, there existed four fracturing locations for harvested fruit, as the frequency increased. Furthermore, the fracturing in the ear and stem was the most important form of fracturing, and microscopic observations revealed that it had a thinner and tidier cell wall and cell cavity. Keywords: Sapindus, Fruit removal force, Vibration, Microstructure.

Air-cooled finned heatsink (FHS) are more compact than water-cooled heatsink due to no water channel, which is beneficial to simplify the structure of the cooling side of the thermoelectric generator (TEG) system. Therefore, a mini channel finned heatsink (MCFHS) was designed in this study based on Venturi effect. In this study, the mathematical model of TEG with MCFHS and FHS were developed and verified. The effects of the heating temperature and air flow velocity around the heatsinks on the TEG performance were analyzed and demonstrated. The TEG performance was investigated in terms of the temperatures of the two sides of the TEG, the TEG voltage, and the TEG efficiency. The results revealed that the smaller thermal resistance of heatsink is favorable for greater output of TEG. And the use of the MCFHS can effectively improve the performance of the TEG under different conditions. The maximum TEG efficiency with MCFHS could be 155% higher than the TEG with FHS.

The present work proposes that there is internal friction and compressive deformation in the primary zone. Mathematical model was established, in which the internal friction coefficient and some compressive characteristics of serrated chips were calculated. High-speed orthogonal cutting experiment was performed on SiCp/Al composites at cutting speeds of 10–350 m/min and feed rates of 0.07–0.12 mm/r. The internal friction and compressive deformation in the primary zone were investigated by combing results obtained in the experiments with the mathematical model. The internal friction coefficient (0.21–0.47), compressive stress (185.4 MPa–226.9 MPa), and compressive strain rate (0.013×104 /s–0.554×104 /s) increased with increasing cutting speed. However, the compression value (17.3 µm–50.0 µm) and compressive strain (0.18–0.26) decreased with the cutting speed.

The viscoelastic behavior of Sapindus mukorossi pericarp (the covering of the Indian soapberry fruit) was investigated. Samples were subjected to creep-recovery and oscillatory shear tests. The moisture content had a strong effect on the dynamic moduli, whereas the temperature had little effect. Both the storage and loss moduli had a weak dependency on the frequency. In general, the storage and loss moduli decreased and slowly converged with an increase in the moisture content. The storage and loss moduli decreased with an increasing temperature. The creep-recovery experiment and dynamic shear tests indicated that the pericarps with high moisture contents were more prone to permanent deformation. The dynamic shear tests further demonstrated that a low moisture content, temperature, and frequency resulted in the pericarps having a more solid behavior and undergoing elastic deformation. Images of the microstructure showed that cells in the raw pericarps were round, of similar size, and neatly arranged. In the treated pericarps, the cells gradually became smaller and finally disappeared. It was inferred that drying with hot air caused the loss of intracellular substances, which in turn strengthened the dynamic characteristics of the pericarps. The completely dried pericarps thus behaved as strong viscoelastic solid in contrast to the raw pericarps.

The mechanism of serrated-chip formation is a basic theoretical foundation for metal cutting. Much research has concentrated on the shear formation characteristics of serrated-chip formation. However, compression deformation has not been proposed to elucidate serrated-chip deformation within the primary zone. This paper proposes a computational model considering compression deformation in the primary zone. Compression deformation characteristics are obtained by combining the model with the results of a high-speed orthogonal cutting experiment. In a high-speed orthogonal cutting experiment on Ti-6Al-4V at cutting speeds of 10–160 m/min and feed rates of 0.07–0.11 mm/r, the compression stress (1134–1600 MPa) decreased with the cutting speed and feed rate. The compression strain (0.10–0.22) and strain rate (0.09 × 104/s–0.75 × 104/s) increased with the cutting speed and decreased with the feed rate. The temperature of the primary zone (272.3–417.2 °C) increased with the cutting speed and feed rate.

Cupronickel B10—an important material widely used in the aero industry—has excellent mechanical and physical properties, such as corrosion resistance and ductility. The present study conducted a quasi-static test and split Hopkinson pressure bar (SHPB) test to obtain the quasi-static and dynamic mechanical properties of cupronickel B10, respectively. In these two experiments, the parameters needed for material constitutive models in cutting simulation are derived. However, the impact deformation temperature in the SHPB experiment has long been ignored, resulting in insufficient simulation accuracy. Hence, the impact deformation temperature is referenced to modify material constitutive models. Simulation results of the models are validated in orthogonal cutting experiments. Validation shows that Johnson-Cook class models are superior in simulating the chip form while Drucker-Prager class models are suitable for forecasting the cutting force and temperature. In particular, modified Drucker-Prager models can reduce the error of cutting force FC to 18.01 %.

The shear angle is one of the important factors in cutting deformation and the shear angle theory reveals the relationship between the shear behavior in the primary zone and the tool-chip friction behavior in the secondary zone. In order to deepen the understanding of shear angle theory, the study investigated the shear angle variation in aluminum alloy Al6061-T6 and compared the three conventional shear angle models, Merchant, Lee and Shaffer, and Hucks. To obtain the shear angle more conveniently, a simple approach utilizing the connection between the shear angle and chip thickness was proposed. Orthogonal cutting experiments were conducted on aluminum alloy Al6061-T6. A new cutting simulation model for shear angle and chip thickness of Al6061 with errors below 15% and 10% respectively was proposed in the study. What’s more, it was found that the three shear angle models have their applicable ranges in cutting speed for the aluminum alloy. It is mainly because the internal friction coefficient of workpiece material decreased as cutting speed rose.

Thermoelectric (TE) materials play an important role in energy production and utilization, but the temperature dependence of material properties makes theoretical analysis challenging. In this work, the TE differential equation is solved by introducing the volume average of TE material parameters, and a simplified TE element model is established for a TE element with a linear temperature profile. The temperature dependence of the Seebeck coefficient, electrical resistivity and thermal conductivity are incorporated into the thermal conductivity equation, and the TE conversion efficiency is solved. This proposed model is applied to a high-performance N-type half-Heusler alloy, and the obtained maximum conversion efficiency agrees well with the numerical results (with relative error 1.36%) for an average temperature Tm = 510 K and temperature difference ΔT = 440 K. The results confirm that the proposed model, which incorporates the Thomson effect, is simple and accurate, providing valuable guidance for optimal performance design of TE devices.

Cupronickel B10—an important material used in aircraft carriers—exhibits excellent electrochemical and mechanical properties, such as high corrosion resistance and weldability. The Split-Hopkinson pressure bar (SHPB) test is a classical method to obtain the dynamic mechanical properties of solid materials. However, the deformation temperature has long been ignored in SHPB studies, which results in low accuracy of the material constitutive model. Thus, in this study, a new method for obtained the deformation temperature was proposed and the modified material equation was validated using experimental data. Quasi-static compression and SHPB experiments were conducted with a thermocouple. The results revealed that the deformation temperature of the quasi-static tests was nearly zero, whereas that of the SHPB experiments ranged from 40 to 90 °C. Therefore, the method developed to describe the deformation temperature can be used to improve the precision of SHPB experiments, as demonstrated for the case of cupronickel B10.

The titanium alloy Ti-6Al-4V has superior properties but poor machinability, yet is widely used in aerospace and biomedical industries. Chip formation and cutting zone area are important factors that have received limited attention. Thus, we propose a high-speed orthogonal cutting model for serrated chip formation. The high speed orthogonal cutting of Ti-6Al-4V was studied with a cutting speed of 10-160 m/min and a feed of 0.07-0.11 mm/r. Using theoretical models and experimental results, parameters such as chip shape, serration level, slip angle, and shear slip distance were investigated. Cutting zone boundaries (tool-chip contact length, length of shear plane, and critical slip plane) and cutting zone area were obtained. The results showed that discontinuous, long-curling, and continuous chips were formed at low, medium, and high speeds, respectively. Serration level, shear slip distance, and slip angle rose with increasing cutting speed. The length of shear plane, tool-chip contact, and critical slip plane varied subtly with increased cutting speed, and rose noticeably with increased feed. Cutting zone area grew weakly with increased cutting speed, levelling off at high cutting speed; however, it rose noticeably with increased feed. This study furthers our understanding of the shear slip phenomenon and the mechanism of serrated chip formation.

To efficiently harvest environmental micro-energy from shallow soil, simulated analysis, theoretical arithmetic and experimental verification are performed to explore the spatiotemporal rules of heat transfer on a soil/finned tube interface. Simulations are carried out for 36 types of different working conditions, and the empirical formulas for temperature and heat flux are obtained. The temperature and heat flux can be calculated using the formulas if the soil temperature, soil moisture content and finned tube initial temperature are known. The simulations also show that the highest heat flux can reach approximately 0.30 mW/mm2, and approximately 1507.96 mW of energy can be harvested through the finned tube. Theoretical arithmetic indicates that the heat transfer rate of the copper finned tube is 76.77% higher than that of the bare tube, the highest rate obtained in any study to date. Results also show that the finned tube should be placed where the soil moisture is greater than 30% to get more heat from the soil. A field experiment is carried out in the city of Harbin in Northeast China, where a thermoelectric power generation device has been installed and temperature data have been monitored for a certain time. The results are in good agreement with those obtained from the simulation analysis. The heat transfer processes and heat transfer steady state on the soil/finned tube interface are revealed in this work and are of great importance for the use of geothermal energy.

A floating power generation device is designed and fabricated to overcome the power supply limitations of wireless sensor networks for environmental monitoring. Once there is a temperature difference between the upper surface exposed to sunlight and the lower surface in the water, the device is capable of generating power while floating in the wetland environment. Fresnel lenses were applied to concentrate solar irradiation on a selective absorbing coat. Meanwhile two vertical axis rotors were used to cool the cold side of the thermoelectric power generator by catching the breeze. The effects of solar irradiation, temperature distribution, load resistance, wind speed, the maximum power and the electrical efficiency of the thermoelectric power generator were analyzed. When subjected to solar irradiation of 896.38 W/m2, the device generated a potential difference of 381.03 mV and a power output of 8.86 mW via thermoelectric generation. In addition, compared with the system without wind, the output power was increased by approximately 10.96% in our system. The low power wireless networks, used in wetland environments, could be operated by the thermoelectric power generated by the floating device. Besides, this system offers powering solution for self-power miniature devices that are applied in aqueous environment.

Friction behavior is an important component of the metal-cutting mechanism. A simple and effective friction device that can yield the desired friction characteristics is required. In this article, a friction device with a solid–liquid–gas vibration reduction was proposed to research the interface friction characteristics. The interface friction characteristics of cupronickel B10 and YG6 were obtained through the new friction device, including the friction force, friction temperatures, and friction coefficient. The results show that an experimental solid–liquid–gas vibration reduction is feasible and effective to obtain the interface friction characteristics. The relationship between the friction-interface temperature T2 and the measured-point temperature T1 that was obtained by a heat-conduction model is linear. For cupronickel B10 and YG6, the friction coefficient gradually decreases with an increase in friction speed, and increases initially and then decreases with an increasing load. Based on the effect of friction temperature, friction speed, and load, a friction model for the interface friction characteristics of cupronickel B10 and YG6 was obtained.

Tool–chip friction of high-speed cutting (HSC) is complex and involves nonlinear problems. This paper proposes a new friction model having multiple factors for HSC and investigates the multiple effects affecting the tool–chip friction coefficient. An experimental method of high-speed friction and an inverse method of obtaining the temperature of the friction interface are proposed. The proposed friction model reveals the inherent relationship between the friction coefficient and the multiple factors, and describes tool–chip friction in the HSC of aluminum alloy 6061-T6 accurately and improves the cutting simulation accuracy. It is also found that an increase in friction speed increases the friction coefficient and that an increase in friction temperature reduces the friction coefficient. However, an increase in ambient temperature clearly increases the friction coefficient at high temperature, and an increase in the normal load reduces the friction coefficient at low temperature and increases the friction coefficient at high temperature. The results provide a clear understanding of the mechanisms of friction speed and temperature, the ambient temperature, and the actual contact area in tool–chip friction of HSC.

Material constitutive model is one of the basic scientific fundamentals for simulation accuracy of high-speed cutting (HSC). A high-speed orthogonal cutting method (HS-OCM) based on the shear slip distance, aided by split Hopkinson pressure bar (SHPB) experiments, is proposed in this paper to obtain the shear slip deformation characteristics in the HSC of 6061-T6 aluminum alloy. The Johnson–Cook (JC) model was modified in three ways according to the variation tendencies of the effect curves of strain hardening, strain rate strengthening, and thermal softening, and an improved material constitutive model was obtained. The simulation validations of the obtained material constitutive models were executed. It was found that the modified JC model improves simulation accuracy, i.e., the maximum simulation errors of the cutting force and cutting temperature are 18.5 and 12.2 %, respectively. The HS-OCM avoids the cutting speed limitation (

Chip formation, an important aspect of the high-speed cutting (HSC) mechanism, is generally accepted as the result of shear deformation in the shear zone and tool-chip friction. In order to accurately study chip formation process in HSC, a theoretical model for the high-speed orthogonal cutting of aluminum alloy 6061-T6 was built, which can be used to calculate the important parameters of chip formation, such as shear angle, friction angle, length of shear plane, tool-chip contact length, and width of the first shear zone. A series of orthogonal cutting experiments, with the YG6 carbide tool and on a wide range of cutting speed (100–1,900 m/min) and feed (0.06–0.15 mm/r), were performed in order to obtain the parameters required in the model, including the cutting forces, the chip thickness, and the shear slip distance. Seven kinds of chip formation parameters were obtained with different cutting parameters in the experiment, and the built theoretical model can well explain the formation process and the morphology characteristics of these chips, which proves that the combined method of theoretical model and orthogonal cutting experiment is an effective and easy approach to obtain the parameters of chip formation in HSC, avoiding the cutting speed limitation and the safety risk in quick-stop test. Within the range of parameters set in the experiments, the chip mainly appears to be continuous chip, curling chip, or discontinuous chip. And the chip thickness, friction angle, length of shear plane, and width of the first shear zone decrease with the increase of the cutting speed; meanwhile, the shear slide distance and shear angle increase.

A two-phase closed thermosyphon is an efficient heat transfer element. The heat transfer process of this type of thermosyphon includes conduction and convective heat transfer accompanied by phase changes. Variations in the inclination angle of a thermosyphon affect the steady-state heat transfer performance of the device. Therefore, the inclination angle is an important factor affecting the performance of a thermosyphon. In this paper, an equation for the actual heating area variations with respect to the inclination angle is deduced, and a model for the areal thermal resistance of a thermosyphon is proposed by analyzing the main influence mechanisms of the inclination angle on the heat transfer process. The experimental results show that the areal thermal resistance, which accounts for the effect of the actual heating area, does not change with respect to the inclination angle and exhibits a linear relationship with the heat transfer rate. The thermal resistance equation is fit according to the experimental data when the inclination angle of the thermosyphon is vertically oriented (90&deg, ), and the predicted values of the thermosyphon&rsquo, s thermal resistance are obtained when the thermosyphon is inclined. The deviations between the experimental data and predicted values are less than &plusmn, 0.05. Therefore, the theoretical equation can accurately predict the thermosyphon&rsquo, s thermal resistance at different inclination angles.

The choice of reasonable cutting parameters is very important for the application of high speed cutting technology. Cutting parameters optimization is a contradiction optimization problem of multi-objectives including cutting efficiency, tool wear and machining quality etc. In order to simplify the complicated problem, a new dimensionless comprehensive evaluation method of cutting parameters based on cutting multi-dimension characteristics including cutting force, temperature, feed rate and cutting depth is put forward in the paper. Then multi-level weight decomposition method is applied to determine the evaluation factors. The relations between multi-objectives and cutting force and temperature are emphatically analyzed. In combination with cutting process physical FEA (finite element analysis) simulation, the effect laws of cutting parameters to cutting force and temperature is researched. Furthermore cutting parameters are evaluated and optimized through the established comprehensive evaluation method. As shown the results: The results obtained by comprehensive evaluation method are match with the results by plenty of cutting experiments. The comprehensive evaluation method is suitable for actual production application because of its simple, effective and extensive characteristics.