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Hybrid supercapacitors represent a promising candidate for grid-scale energy storage devices because of their excellent high-power density, inherent safety and low cost. Here we report a novel NiSe2@rGO nanocomposite (reduced graphene oxide decorated NiSe2 nanoparticles), which shows high specific capacity of 467 C g-1 at 1 A g-1 and superior rate performance (∼72.8 % of the capacity retention at 20 A g-1). Moreover, a hybrid supercapacitor (HSC) assembled from the NiSe2@rGO positive electrode and rGO negative electrode delivers high energy density (34.3 Wh kg-1) and splendid cycling lifespan (∼93% of the capacity retention over 6500 cycles). This study provides a novel insight on high-performance hybrid supercapacitors.

Objective . A case study was used to discuss the effects of Traditional Chinese Medicine (TCM) treatments on Sjogren's syndrome. Clinical features and outcomes . A 45-year-old woman suffered from dry eyes, dry mouth, and fatigue for six months and was diagnosed with Sjogren's syndrome. She had received regular treatment with hydroxychloroquine (HCQ) and artificial tears as well as artificial saliva for nearly one year, but the results were unsatisfactory. Therefore, she sought CHM for further intervention. After 7 months of Yi-Guan-Jian with Huai-Xiao-Mai (Triticum aestivum Linn.) and Tian-Hua-Fen (Trichosanthis Radix), on the seventh treatment with TCM, she reported no fatigue or sleep dysfunction and relief of dry eyes and mouth. Neither complications nor side effects were noted during the CHM treatment. Conclusions . From this case, we concluded that CHM may be an effective and safe alternative therapy for the treatment of Sjogren's syndrome.

Searching for low-cost, high capacity, stable and well-designed cathode materials with good rate capability and long-life cycling performances is our long-term goal for rechargeable lithium/sodium batteries. In this work, a simple and scalable strategy is developed to synthesize metal-organic frameworks (MOFs) derived Fe7S8/C composites by sulfurizing Fe-MIL-88A MOFs. The synthesized Fe7S8/C composites are of rod-like morphology with the well-dispersed Fe7S8 nanoparticles in porous carbon matrix. Such a structure could offer distinct advantages for Fe7S8-based electrode materials for both lithium and sodium batteries. When evaluated as a cathode material for rechargeable Fe7S8/Li batteries, the Fe7S8/C composites exhibit a long and flat discharge plateau around 1.5 V and delivers a high specific discharge capacity of 473 mA h g−1 at 0.1 A g−1 after 100 cycles with excellent rate capability and long-life cycling performance at high current density (~301 mA h g−1after 1000 cycles at 1.0 A g−1). Moreover, the Fe7S8/C composites could also exhibit high specific capacities, good rate performance and high cycling stability as an anode material for sodium ion batteries. Our findings demonstrate that Fe7S8/C composites with rod-like morphology are promising electrode materials for lithium/sodium batteries.

So far the amount of artistically interesting drawings similar to Circle Limit I-IV is very limit. Still a few examples created by M.C. Escher are the outstanding hyperbolic arts. Based on hyperbolic geometry and computer graphics techniques, this article presents an easily-reproducible approach to generate drawings similar to Circle Limit I-IV. To create more kinds of elegant hyperbolic drawings, several conformal mappings are proposed to transform disc drawings into some special domains. The method can be used to create a great variety of hyperbolic drawings.

Monolayer diamond grinding tools are commonly made by electroplating or brazing. However, electroplated tools involve weak grain/matrix adhesion due to a lack of chemical bonds, and brazed diamonds often suffer thermal damage resulting from the high-temperature brazing process. This paper reports a new method to fabricate monolayer diamond grinding tools by chemical vapor deposition (CVD) technique. First, diamond powders at the range of 7–180 μm are chosen as seeds of the abrasive grains. The seeds are randomly distributed on SiC substrates by spraying the suspension containing the seeds toward the substrates in a spin coater machine, or orderly positioned on the substrates by a patterned mask. Then CVD diamond growth is conducted on both the substrates and the seeds simultaneously. As-grown diamond films on the substrates are regarded as bonding layers of the grinding tools, and the original seeds with irregular and crushed morphologies can grow into blocky cube-octahedral grains with smooth surfaces, which are supposed to have enhanced mechanical strength. Raman spectra demonstrate that as-grown diamonds on both the substrates and the seeds are of high quality and low levels of graphitization. Besides, relatively low residual stresses are detected in the diamond grains, because both the bonding layers and the grains are made of diamond. Grinding tests are conducted using as-fabricated CVD diamond grinding tools and electroplated/brazed diamond grinding tools as comparisons. The results suggest that the CVD diamond grinding tools possess the best wear resistance in terms of the fracture of the diamond grains. This is attributed to the epitaxial grain structure that restrains the crack propagations. In addition, the wear of the CVD diamond grains can generate tiny pyramidal crystalline tips and sharp edges, indicating the unique shelf-sharpness during the grinding.

The congestion effect refers to the phenomenon that more customers choosing to use the same facility reduces the facility’s utility. This work addresses the optimal pricing problem for a firm operating a joint-venture terminal under the congestion effect. The firm is formed between a port terminal operator and a shipping line, thus being able to provide a bundle of ocean transportation and port terminal solutions to cargo suppliers. The objective is to determine the optimal prices charged to cargo suppliers to maximize the total profit of the firm. First, we develop a tractable flow-based optimization model that uses a fixed-point equation to capture the interaction between the congestion effect and cargo suppliers’ choice. Second, we characterize the optimal solution for a variety of cases, including the single origin-destination case, partially homogeneous case that includes the fully homogeneous case as a special case, and heterogeneous case. Third, we evaluate the profit loss incurred by ignoring the congestion effect with numerical studies. Moreover, we propose one-variable and two-variable search methods for the partially homogeneous and heterogeneous cases, respectively. We learn that the firm should quote the same price to all cargo suppliers under the fully homogeneous case. However, this is not necessarily optimal under the partially homogeneous or heterogeneous cases. The profit loss incurred by neglecting the congestion effect can be significant and increases as cargo suppliers become less tolerant of congestion.

The frictional resistance and hole quality when drilling CFRP laminates are associated with tribological behaviors of drill materials. In the present study, tribological tests are conducted on various diamond coated WC-Co balls sliding against T800/X850 CFRP laminates with [-45/90/45/0]s lay-up, under specific conditions similar to the drilling process. It is firstly found that the coefficient of friction (COF) varies with the sliding direction. The boron-doped micro-crystalline and nano-crystalline composite diamond (BDMC-NCCD) film synthesized by optimized growth durations (9 h for BDMCD and 2.5 h for NCD) presents relatively low COF and wear rate (0.193 and 0.97 × 10−8 mm3/N m, when the sliding velocity and normal load are respectively 1.5 m/s and 5.0 N), as well as high critical load for the film peeling (35 N), owing to the nano-sized diamond grains and low surface roughness (Ra~125.09 nm measured by the confocal microscopy) of the surface NCD layer, and high hardness and favorable adhesion of the underlying BDMCD layer. Besides, influences of the sliding velocity and normal load are clarified, indicating that the COF increases with the load, but decreases with increasing the velocity, while the wear rate increases with either the load or velocity.

The environmental pollution issue of port has been highly concerned about by government and green port has been a focus to sustain the development of maritime transportation. At present, the port operator mainly takes measures of designing reasonable berth allocation for vessels and improving loading/unloading efficiency of quay cranes to reduce the carbon emission of port. The International Maritime Organization (IMO) has proposed to impose carbon emission tax on ports in the long-term, which would definitely enhance the willingness of ports to reduce the carbon emission. Therefore, this paper makes effort to explore the study of integrated berth allocation and quay crane assignment problem with considering two policies of different carbon emission taxation rates on port: one is unitary taxation rate and the other is piecewise taxation rate. Two corresponding mathematical optimization models are proposed for the two policies respectively and a number of equivalent or relaxed models are developed to ease the models. Finally, a set of test instances are randomly generated to access the applicability of the proposed models and an actual case is implemented to evaluate the effect of imposing carbon emission taxation on carbon emission reduction. It is found that the carbon emission taxation policy has significant effect on berth-QC plans and the carbon emission can be significantly reduced.

In this work, a comparative study of diamond films consisting of alternate microcrystalline (MCD) and nanocrystalline diamond (NCD) layers is conducted. Diamond films including monolayer, bilayer and multilayer diamond films are coated on cemented tungsten carbide (WC-Co) substrates by adopting a bias-enhanced hot filament chemical vapor deposition (HFCVD) technique. Tribological properties of the diamond films are evaluated by using a reciprocal tribometer without lubrication. Further milling tests are carried out to examine the cutting performances with sintered zirconia ceramics as workpiece comparatively. In friction test against zirconia ceramics, the monolayer NCD film shows the lowest friction coefficient (0.128) because of its smooth surface. Also, the bilayer diamond film with surface coating of NCD layer (MNCD) and both of the multilayer diamond films exhibit good friction property while the monolayer MCD film has the largest friction coefficient (0.292). The milling test demonstrates that the monolayer diamond (MCD and NCD) coated milling tools show poor tool life due to abrasive action of hard workpiece. Working life of all the bilayer and multilayer diamond coated tools is enhanced, but large area shedding of coatings appears after some milling passes except the multilayer diamond film with surface coating of NCD layer (MNMN-CD). The multilayer film (MNMN-CD) presents superior machining performance and its working life increases by 3–7.5 times compared with the monolayer diamond coated ones.

When drilling the carbon fiber reinforced plastics (CFRP), the tool shape and surface coating both play important roles in the cutting performance, which are complex and comprehensive, and should be systematically studied. In this research, WC-6wt.%Co drills in typical shapes are prepared, on which high-performance composite diamond films are deposited by the hot filament chemical vapor deposition (HFCVD) method. It is firstly proved by drilling tests that the tool shape always acts as a determining factor that significantly influences the drilling force and machining quality, for either the uncoated or diamond coated drills. The shorter chisel edge, smaller actual point angle and the proper double point angles are all factors in their favor. By contrast, as-deposited diamond films can slightly reduce the drilling force, while sometimes it even deteriorates the hole quality, due to the edge roundness caused by the alkali-acid pretreatment and the film growth. However, the diamond films play critical roles in improving the wear resistance, elongating the lifetime and guaranteeing the stability of the machining quality in the long-duration drilling process. In addition, the tool lifetime is also closely associated with the tool shape, attributed to the different thrust forces, consequently the lifetime of the diamond coated standard twist drill is much shorter than those of all other coated ones.

Nano/microcrystalline composite diamond films were deposited on the holes of WC-6%Co drawing dies by a two-step procedure using alternative carbon sources, i.e., methane for the microcrystalline diamond (MCD) layer and acetone for the nanocrystalline diamond (NCD) layer. Moreover, the monolayer methane-MCD and acetone-NCD coated drawing dies were fabricated as comparisons. The adhesion and wear rates of the diamond coated drawing dies were also tested by an inner hole polishing apparatus. Compared with mono-layer diamond coated drawing die, the composite diamond coated one exhibits better comprehensive performance, including higher adhesive strength and better wear resistance than the NCD one, and smoother surface (Ra=65.3 nm) than the MCD one (Ra=95.6 nm) after polishing at the same time. Compared with the NCD coated drawing die, the working lifetime of the composite diamond coated one is increased by nearly 20 times.

Tribological tests are conducted on diamond films under different lubrications, and influences of film type, lubrication, test parameters on coefficient of friction (COF) and film wear (Id) are studied. Diamond films perform better than WC-Co under water-based emulsion lubrication, and the boron doped micro-crystalline and nano-crystalline composite diamond (BDMC-NCCD) film shows the best overall behavior. Considering the performance and economy, the water content in the emulsion is optimized as about 80 vol%. Under this drawing condition, the quality of the production is similar to that drawn by the uncoated dies under the oil lubrication, however, the coated dies present much prolonged lifetime and lower temperature. Most importantly, the use of the water-based lubrication is much more environmentally friendly.

WS2-modified SnO2 hybrid nanocomposite was synthesized by a hydrothermal method. The morphology and structure characterization revealed that the SnO2 nanocrystals were anchored to the WS2 nanosheets in the homogeneous nanocomposites. The resistive humidity sensors based as-prepared nanocomposites, pure WS2 nanosheets and pure SnO2 microspheres were fabricated and tested in a humidity range of 11–95% RH at 25 °C. The humidity sensing properties of the nanocomposites manifested a good and stable humidity sensing. The response of the hybrid nanocomposite in air with 95% RH was found to be 8.5 and 862.8 times higher than that of pure SnO2 microspheres and WS2 nanosheets, respectively. The synergistic effect between WS2 and SnO2 played an important role in improving the humidity sensing performance of the hybrid nanocomposites.

Based on the traditional deposition technique with the filament through the hole (DTFTH), the growth of high-quality diamond films on inner hole surfaces, especially those with small apertures, is rather difficult and laborious. In the present research, the deposition technique with no filament through the hole (DTNFTH) is proposed, and its feasibility and limitations are discussed on the basis of the radiation computation, temperature simulation, analyses on mean free paths of various active radicals, and the experimental verification of the “shading and distance effects”. It is indicated that the ratio of the hole depth to the hole diameter should be smaller than four. Afterwards, the drawing die with an aperture of 2 mm is designed, and a case study focusing on a single die and the mass production of diamond coated dies by the DTNFTH are both accomplished, using optimized deposition parameters. It is demonstrated that the film thicknesses are in the range of 4.8–6 μm (case study) and 3.5–5 μm (mass production), showing acceptable uniformity. Uncoated, DTFTH- and DTNFTH-diamond coated dies are all submitted to field tests, indicating that the lifetime of the DTFTH-diamond coated die is approximately eight times more than that of the uncoated one, while the DTNFTH-diamond film prolongs the lifetime of the uncoated die by a considerable factor of five.

Systematical researches were accomplished on WC–Co with different Co contents (6%, 10% and 12%, mass fraction). Based on the XPS and EDX, from orthogonal pretreatment experiments, it is indicated that the acid concentration, the time of the acid pretreatment and the original Co content have significant influences on the Co-removal depth (D). Moreover, the specimen temperature, original Co content and Co-removal depth dependences of the Co evolution in nucleation, heating (in pure H2 atmosphere) and growth experiments were discussed, and mechanisms of Co evolutions were summarized, providing sufficient theoretical bases for the deposition of high-quality diamond films on WC–Co substrates, especially Co-rich WC–Co substrates. It is proven that the Co-rich substrate often presents rapid Co diffusion. The high substrate temperature can promote the Co diffusion in the pretreated substrate, while acts as a Co-etching process for the untreated substrates. It is finally found that the appropriate Co-removal depth for the WC–12%Co substrate is 8–9 μm.

The drilling performance of four typical types of single-layer diamond coated drills and two-layer boron-doped-microcrystalline/nanocrystalline diamond (BDMC-NCD) composite coated drill is compared, and the growth duration ratio of the NCD layer to the BDMCD layer ( N/B ) is optimized. It is demonstrated that the BDMC-NCD film synthesized using proper N/B shows nice adhesion, moderate diamond quality and a smooth surface mostly composed of nano-sized diamond grains, so it shows the best comprehensive performance, including the thrust force reduction, the improvement of the hole quality, the slowing of the tool wear and coating peeling, and the elongation of the tool lifetime. Taking the time of the coating peeling into consideration, 3/9 is the optimum N/B for the BDMC-NCD coated drill, and such the drill also performs the longest lifetime using delamination factors ( F d ) of 1.2 or 1.3 as the failure criteria. Moreover, the failure mode of the diamond coated drill is the flank wear when using F d = 1.1 or 1.2 as the failure criteria, while the tool failure should be related to the coating peeling when F d = 1.3.

Silicon-based anodes with carbon materials as current collectors are promising for the fabrication of flexible lithium-ion batteries with high energy density due to the high specific capacity of silicon as well as the light weight and excellent flexibility of carbon materials. Currently it is still significant and challenging to develop new preparation methods and electrode structures to achieve the combination of low cost and high performance for such anodes. In this work, we report a simple and scalable method to prepare freestanding and flexible CNT/(Fe@Si@SiO2) composite anodes with novel kernel-pulp-skin nanostructure for lithium-ion batteries. This unique kernel-pulp-skin nanostructure facilitates the charge transfer at the electrolyte/electrode interface and the diffusion of lithium in the electrode material, which significantly improves the cycle stability and rate capability of the electrode. The resultant CNT/(Fe@Si@SiO2) composite anodes exhibit a high reversible capacity (968 mAh g−1 at 1 A g−1) and stable cycling performance with a capacity retention of 83% after 500 cycles.

Ultrananocrystalline diamond (UNCD) coating possessing low surface roughness was innovatively deposited on printed circuit board (PCB) end mills in order to improve the surface smoothness and prolong the tool duration while machining 5G PCB material. Six types of diamond coatings, involving microcrystalline diamond (MCD), nanocrystalline diamond (NCD), ultrananocrystalline diamond (UNCD), microcrystalline diamond/nanocrystalline diamond (MCD/NCD), microcrystalline diamond/ultrananocrystalline diamond (MCD/UNCD), microcrystalline diamond/nanocrystalline diamond/ultrananocrystalline diamond (MCD/NCD/UNCD), were synthesized on PCB end mills. The Raman spectrum of diamond coatings were obtained to characterize the phase composition, illustrating that Raman spectra of UNCD, MCD/UNCD and MCD/NCD/UNCD present “M” shape, including dominant D peak and G peak. The adhesion levels were assessed, showing that the bottom MCD layer helps to improve the adhesion of MCD/NCD, MCD/UNCD and MCD/NCD/UNCD on WC-Co substrates and MCD/NCD/UNCD can suppress effectively the crack propagation. Moreover, the tribological properties and wear performances of these diamond coatings were compared. The comparison results of friction coefficients are in good accordance with those of surface roughness. The superior adhesion of bottom MCD, the elegant transition of middle NCD and the low friction coefficient of the top UNCD lead to the outstanding wear performances of MCD/NCD/UNCD coated end mill while machining PCB slots.

Manganese oxides are regarded as promising cathode materials for aqueous zinc ion batteries (ZIBs) due to their low cost and high theoretical capacity. However, their practical application is seriously hindered because of the inferior electronic conductivity, sluggish diffusion kinetics and structural instability. Herein, we develop a new K-preintercalated MnO2 (K0.19MnO2·0.56H2O, KMO) nanosheet by a facile hydrothermal method. Preintercalation of K+ ions into the MnO2 crystal layers with structural reconstruction can activate more active sites, strengthen the crystal structural stability and facilitate the insertion/extraction of Zn2+ ions. The charge shielding effect of crystal water promotes the diffusion kinetics of Zn2+ ions. The obtained KMO electrode delivers high specific capacity (107 mAh g−1) and good cycling stability (~87.5% capacity retention after 2000 cycles), revealing its potential application for aqueous ZIBs.

In the present study, at fixed hydrogen flow rate of 400 sccm, we demonstrate the coupling effects of methane/hydrogen ratio ηC (7.5– 15 vol%) and nitrogen flow rate fN (0– 0.9 sccm) on morphologies, mechanical properties and tribology behaviors of the diamond films deposited on cemented carbide (WC-Co) substrates. At lower ηC (7.5 vol%), increasing fN from 0 to 0.9 sccm leads the diamond film to transform from 〈110〉-oriented to 〈110〉- & 〈100〉-oriented. Besides, increasing ηC accelerates the orientation transition, i.e., {110} and {100} crystallographic planes can be formed at even lower nitrogen addition level. Furtherly increasing ηC and fN to 15 vol% and 0.9 sccm, the film morphology transforms to nanocrystalline diamond (NCD). Moderate nitrogen addition acting as a catalyst at the substrate surface increases the growth rate, by the mechanism of promoting the individual grains growth. However, supersaturated nitrogen will suppress the growth of individual grains by generating masses of secondary nucleation on the crystal faces, resulting in a slight reduction of the growth rate. The 〈110〉- & 〈100〉-oriented diamond film deposited at ηC = 7.5 vol% and fN = 0.9 sccm and the NCD film both present low small surface roughness and coefficient of friction (COF) when sliding against the Si3N4 balls, while the former has higher hardness and Young's modulus, along with lower wear rate and better adhesive strength, which has great potential for the application as wear-resistant and anti-friction coating.

Cylinder covers of diesel engines with complex structures may be contaminated by multiple contaminants, which can hardly be efficiently removed by traditional cleaning methods, and those methods may do harm to environment and human body. Fortunately, such drawbacks can be overcome by the molten salt cleaning (MSC). In the present study, it was proven that the cleaning effect of the MSC was fairly good, and the mechanism was explained by analyzing compositions and morphology of the contaminants and gas production. The contaminants could be divided into two categories: the black deposition of the organic matters in oil channels (40 μm in thickness, containing hydroxide radical and aromatic groups), and the incrustations in water channels (20 μm in thickness, consisted of CaCO3). The gas production was consisted of complex compositions, including alkanes, olefins, aromatic hydrocarbons, aldehydes, esters, alcohols, ketones and hydroxyl. Based on above analyses, it was believed that the cleaning mechanism included the thermal effect, physical flow effect, along with the pyrolysis/oxidation reactions. Thermo-gravimetric analysis (TGA) tests were conducted on either the black deposition or salt-deposition mixtures, in either the air or nitrogen atmospheres, for sake of analyzing the clean dynamic. The total weight loss of the mixtures in the air was 92.816%, and the activation energy was 150.06 kJ/mol. It was concluded that the oxidation effect was almost negligible for the contaminants only, which however accounted for 15.9688% of the contaminants removal in the presence of the molten salt.

This work considers the stochastic resource allocation problem for single-leg transportation markets with service disruptions. The single-period version of the problem is formulated as a stochastic model with arbitrarily distributed resource capacity. We then completely characterize the optimal solution to the stochastic model. The multi-period version of the problem is formulated as a dynamic programming model. We characterize the monotone structure of the optimal solution for the dynamic model under uniform resource consumption rates. For the case with general resource consumption rates, a counterexample is provided to show that there exist cases where the optimal solution is not monotone.

This paper investigates a dynamic resource allocation problem, in which an intermodal operator attempts to determine the policy that characterizes the optimal quantities of each service product allowed to be sold during each time interval within a finite selling horizon. The problem is formulated as a Markov decision process (MDP) model and a variety of mathematical programming models are developed to approximate the MDP model. A series of policies are obtained from the optimal solutions to the approximation models and theoretical results are provided to characterize the comparisons between the MDP model and the approximation models. Various policies are further evaluated through theoretical analysis and simulation tests. We finally gain insights into the importance of the dynamic decisions, stochastic demands, model re-solving, and integer variables in formulating approximation models.

Sandblasting combined with acid etching was utilized as pretreatment of Co-cemented tungsten carbide substrates for the deposition of chemical vapor deposition (CVD) diamond films. Diamond films were deposited on the pretreated surface as well as on substrates treated by a two-step alkali-acid pretreatment as a contrast. The field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), Raman spectroscopy, Rockwell hardness tester and turning test were respectively conducted to characterize the pretreated substrates and deposited diamond films. Surface roughness of the treated surface was controlled by adjusting sandblasting parameters. An enhancement of surface roughness and removal of the binder phase were detected on the treated surface. The porous Co-depleted carbide layer caused by sandblasting and acid-etching pretreatment was obviously thinner compared to the two-step pretreatment. The nucleation stage of CVD process was investigated and the nucleation density was obviously enhanced by the sandblasting pretreatment. Indentation tests exhibited an improvement of adhesive strength compared to the two-step pretreatment. Moreover, the XRD patterns showed that the residual stress of diamond films was decreased. The turning tests showed that the diamond coated tools with sandblasting-acid pretreatment exhibited less area of flank wear and film shedding.

For the chemical vapor deposition (CVD) of diamond films, boron doping with appropriate boron doping levels can enhance the basic mechanical properties of the as-deposited films, especially the film-substrate adhesive strength. However, the boron doping level, which is thought to play a critical role in modifying the properties of the boron-doped diamond (BDD) film, must be further investigated. In the present investigation, the commonly used reaction-bonded silicon carbide (RB-SiC) material is selected as the substrate upon which boron-doped micro-crystalline (BDMCD) films with similar film thickness (24.8–26.3 μm) are synthesized using mixed reactant gas with different B/C atomic ratios, i.e., different boron doping levels. Systematic characterization and solid particle erosion tests are conducted on all specimens to elucidate the influence of the boron doping level on the diamond films' basic mechanical properties and erosion behavior and to elaborate the impact velocity and impact angle dependence of the erosion behavior. The results demonstrate that moderate boron doping levels (5000 and 8000 ppm) are able to maximize the growth rate, reduce the surface roughness, guarantee diamond quality and hardness, minimize the residual stress, and significantly enhance the film-substrate adhesive strength, thereby providing favorable erosion behavior. By contrast, very high boron doping levels (12,000 and 16,000 ppm) deteriorate the erosion behavior of as-deposited BDMCD films, mainly because of the excessive reduction of the film quality and hardness, together with the deterioration of the film-substrate adhesive strength caused by the transformation of the residual stress from compressive to tensile. With increasing either impact velocity or impact angle, the stable erosion rates of all specimens increase, and the film lifetime of the coated specimens become shorter. Moreover, the impact velocity dependence of stable erosion rates for diamond-coated specimens is considerably stronger than that for the uncoated RB-SiC specimen, as indicated by a much higher velocity exponent.

We consider a discrete intermodal network design problem for freight transportation, in which the network planner needs to determine whether or not to build up or expand a link to minimize the total operating cost of carriers and hub operators under a general route choice model of intermodal operators. We formulate the problem as a mixed-integer nonlinear and non-convex program that involves congestion effects, piecewise linear cost functions, and a fixed-point constraint. We develop a series of relaxed and equivalent models to reduce the hardness of the problem and provide theoretical results to show the equivalences. We present two solution methods to solve the problem with one returning heuristic solutions and the other generating a globally optimal solution. We offer two numerical experiments to test the two solution algorithms and also shed light on their performance comparisons.

We study the seat allocation problem for passenger rail revenue management, in which a rail operator attempts to determine the optimal quantity of seats to be allocated to each cabin class for each train service. We formulate the problem with single-stage and multi-stage decisions as two stochastic programming models that incorporate passengers’ choice behavior. We transform the stochastic models into equivalent deterministic mathematical programs that are easy to solve. Then, we form a variety of seat allocation polices from the optimal solutions to the seat allocation models. A number of simulation tests are offered to test the policies.

Chemical vapor deposition (CVD) diamond films have been widely applied as protective coatings on varieties of anti-frictional and wear-resistant components, owing to their excellent mechanical and tribological properties close to the natural diamond. In applications of some components, the inner hole surface will serve as the working surface that suffers severe frictional or erosive wear. It is difficult to realize uniform depositions of diamond films on surfaces of inner holes, especially ultra-large inner holes. Adopting a SiC compact die with an aperture of Ф80 mm as an example, a novel filament arrangement with a certain number of filaments evenly distributed on a circle is designed, and specific effects of filament parameters, including the filament number, arrangement direction, filament temperature, filament diameter, circumradius and the downward translation, on the substrate temperature distribution are studied by computational fluid dynamics (CFD) simulations based on the finite volume method (FVM), adopting a modified computational model well consistent with the actual deposition environment. Corresponding temperature measurement experiments are also conducted to verify the rationality of the computational model. From the aspect of depositing uniform boron-doped micro-crystalline, undoped micro-crystalline and undoped fine-grained composite diamond (BDM-UMC-UFGCD) film on such the inner hole surface, filament parameters as mentioned above are accurately optimized and compensated by orthogonal simulations. Moreover, deposition experiments adopting compensated optimized parameters and some typical contrastive parameters are also accomplished for further verifying the rationality of the computational model and the correctness of the compensation coefficient 0.7 defined for the downward translation determined by simulations. More importantly, on the basis of more simulations and verification tests, a general filament arrangement model suitable for Ф50–120 mm circular inner holes is determined, involving all above filament parameters that are functionally dependent on the diameter of the inner hole.

Chemical vapor deposition (CVD) diamond thick film, due to its higher hardness and better wear resistance, is a potential competitor of the poly-crystalline diamond (PCD) when used as the brazed tool tip. Besides, compared with the thin diamond coated tool, the diamond thick film brazed tool does not have the risk of catastrophic coating delamination. However, due to the fragile characteristic of the free-standing diamond thick film, the conventional polishing is complicated and inefficient. In this study, a novel CVD-diamond thick film-Si3N4 brazed WC-Co (i.e. DB) tool is proposed. The diamond thick film was deposited on the Si3N4 substrate by microwave plasma CVD (MPCVD), using the optimized deposition parameters: microwave power = 3.5 kW, reactant pressure = 20 kPa and methane concentration = 10 %. Adopting the sandblasting and nanodiamond seeding pretreatment methods could improve the film surface smoothness and suppress the voids formation on the film-substrate interlayer, which are beneficial for the post polishing process. In addition, Si3N4 as the supportive substrate could help to prevent the diamond film breaking from polishing. The polished CVD diamond thick film-Si3N4 was laser cut to small tips and then brazed on the WC-Co cutter body. The cutting performance of DB tool was tested in dry turning hypereutectic Al-Si alloy, adopting the PCD and thin diamond coated WC-Co (i.e. DC) tools as comparisons. The cutting results suggest that DB tool outperformed the PCD and DC tools in term of service life and surpassed the DC tool in machining quality. Moreover, the novel tool in this study avoided some typical problems for the conventional diamond tools, such as the coating delamination for thin diamond coated tool and preferred wear of the binder for PCD tool. Noteworthy is that the worn DB tool still presents a rather sharp cutting edge, only some micro-columnar diamond crystals chipped from the flank face.

Behaviors of diamond coated Ti-related parts are significantly affected by carbonized interlayers, so it is essential to determine or predict the carbonization depth during diamond growth. Following the Fick’s law of diffusion with carbon concentration-dependent diffusion coefficients, it is roughly predicted that carbonization depths in Ti and Ti–6Al–4V substrates hardly reach 30 μm within a long duration of 16 h. After trying some characterization methods (XPS, EDS, metallographic analysis and ToF-SIMS), the EDS line scanning is selected as the practical one with sufficient accuracy and convenience. Influences of some critical factors, including growth duration, substrate temperature, reactant pressure and acetone (carbon source) concentration, are studied and discussed. Considering all of the factors, especially those related to the diamond coverage that can suppress carbon diffusion, the modified diffusion models for describing the carbon diffusion, are constructed, defining carbon concentration and diamond coverage (duration, pressure, carbon concentration)-dependent diffusion coefficients. Such the models can be used for well predicting the carbonization depths under most conditions, which are valuable for controlling the carbonized layers during fabrications of diamond coated Ti-related components facing to various applications.

5G printed circuit boards (PCBs), composed of glass fiber, epoxy resin and ceramic, are a kind of difficult-to-machine material. The manufacture of massive high-quality micro holes on 5G PCBs raise high requirements on the tool life and machining precision of PCB micro drills. Chemical vapor deposition (CVD) diamond coatings can be used as effective protective films on PCB micro drills. The surface smoothness and coating-substrate adhesion of diamond coated micro drills are two important factors affecting the drilling performances. Different from previously reported microcrystalline diamond (MCD) or nanocrystalline diamond (NCD) coating types on cutting tools, undoped (UD-) and boron doped (BD-) ultrananocrystalline diamond (UNCD) coatings with higher surface smoothness are firstly applied on PCB micro drills to reduce the friction and cutting resistance and improve the cutting performances while machining PCBs. Moreover, different from the usual argon-rich gas atmosphere for UNCD synthesis, the synthesis mechanisms of UD-UNCD and BD-UNCD with hydrogen-rich atmosphere adopting HFCVD method are clarified. Sufficiently high renucleation rate of diamond crystallites, long mean free path of reactive precursor species and high removal rate of non-diamond carbon phases lead to the successful synthesis of UNCD films. UDMCD, UD-UNCD, UD-MCD/UD-UNCD, BD-MCD, BD-UNCD, and BD-MCD/BD-UNCD, were synthesized on PCB micro drills using HFCVD. The tribological performances and wear mechanisms of these different diamond coatings were studied systematically. The dominant wear mechanism causing tool wear and fracture of diamond coated micro drills in high-speed machining PCBs is abrasive wear. The degree of abrasive wear while machining PCBs are mainly determined by the surface smoothness, surface roughness and coefficient of friction of diamond coatings. The top layer UNCD with tiny grain size leads to the improvement of surface smoothness and tribological properties, which enhance the chip evacuation capacity and reduce the tool wear. Besides, both boron doping and middle layer MCD can contribute to the strong coating-substrate adhesion. Therefore, BD-MCD/BD-UNCD coated micro drill exhibits the best cutting performances while machining PCBs.

H-, O-, OH- and F-terminated N-doped diamond surfaces are calculated by the density functional theory in the present study. Combined effects of terminating species and substitutional N dopants in the 1st or 2nd carbon layers on several critical features (i.e., bond length, total electron density, bond population, atomic charge, Fukui function, and density-of-states) are systematically studied and discussed. The N dopant presents clear, but local, effects for all the terminating species and dopant positions. The adsorption of any individual species to the N dopant in the 1st carbon layer results in the reduction of adsorption energy (less negative), most probably owing to the full shell structure of this N dopant. The H, OH and F each provides one unpaired electron to occupy the antibonding states within the N–H, N–OH and N–F bonds, making the bonds elongated, reducing the corresponding electron densities and bond populations. On the contrary, the N dopant in the 2nd carbon layer induces slight increment of the adsorption energy for O, OH and F, attributed to the positive atomic charges of neighboring topmost C atoms. Amongst the four adsorbates, the O shows the highest reactivity to either an electrophilic or a nucleophilic attack. Besides, N dopants have slight influences on the reactivity of the adjacent adsorbates. The present results can help to understand some related chemical processes (such as the oxidation and electrochemical analysis) on N-doped diamond films.

The study concentrates on systematic investigations on the effects of extremely high or low carbon concentration (2%–14%) and gas pressure (800 Pa–3200 Pa) on crystal structures, grain sizes, phase compositions, surface and cross-sectional morphologies, growth rates, surface roughness, mechanical and tribological performances of various polycrystalline diamond films synthesized on cemented carbide (WC-Co) substrates with hydrogen-rich/argon-lean gas mixture adopting hot filament chemical vapor deposition (HFCVD) method. The crystal structure, grain size and phase composition of various diamond films synthesized with different carbon concentration and gas pressure were analyzed, indicating that as-deposited diamond films cover microcrystalline diamond (MCD), submicrocrystalline diamond (SMCD), nanocrystalline diamond (NCD) and ultrananocrystalline diamond (UNCD). The surface and cross-sectional morphologies of these various polycrystalline diamond films were observed, and the growth rates of various diamond films were calculated. The three-dimensional morphologies and surface roughness were obtained. With increasing the carbon concentration and decreasing the gas pressure during the synthesis, the crystal size decreases so that diamond film with high smoothness, low surface roughness can be obtained. Subsequently, the synthesis mechanisms of MCD, SMCD, NCD and UNCD films with different carbon concentration and gas pressure under hydrogen-rich gas mixture adopting HFCVD were discussed in detail. The elastic modulus and nanohardness of different diamond films were measured quantitatively, and the film-substrate adhesion were evaluated qualitatively. Moreover, the tribological performances of various diamond films synthesized with different carbon concentration and gas pressure were studied by sliding against silicon nitride (Si3N4) ceramic balls. Results indicate that obtaining the dynamic equilibrium between sufficiently renucleation rate of diamond nuclei and effectively removal rate of non-diamond carbon phase by adjusting carbon and gas pressure under the hydrogen-rich gas chemistry can contribute to the synthesis of high-quality UNCD film.

Printed Circuit Board (PCB) filled with a large amount of Alumina ceramics has broad application prospects in the fifth-generation industry but is hard to drill. This work focuses on high-performance diamond films to improve the working life of drilling tools and holes quality of products. By utilizing hot filament chemical vapor deposition (HFCVD) methods, the monolayer microcrystalline diamond (MCD), bilayer micro-nanocrystalline diamond (MNCD), and four-layer diamond (MNMNCD) are coated on commercial PCB drills (WC-6% Co). Solid particle erosion tests are conducted to study erosive wear mechanism of diamond films impacted by ceramic powders/particles. Besides, cutting performances of diamond coated drilling tools are evaluated by performing high-speed drilling tests with PCB as workpieces. In Erosion tests, the monolayer MCD film presents intergranular fracture and shows the lowest erosive resistance. The MNCD and MNMNCD films have similar fracture forms, where curved boundaries and steps between layers indicate their discontinuous fracture, and minor deep cone holes on the surfaces demonstrate their high resistance to crack growth. Moreover, only one minor deep cone hole is observed on the four-layer film which indicates it has the best resistance to particle impinging. In drilling tests, the number of holes drilled by the diamond coated tools before failure is regarded as criteria of working life. Then surface and sectional morphologies of holes are also observed to evaluate the quality of products. The results indicate the number of holes machined by the four-layer MNMNCD coated drills reaches 10,000, while that of the monolayer and the bilayer MNCD ones are 3000– 4000 and 6000 respectively. More importantly, different from the other two types of diamond coated tools, almost no burrs with a height of over 20 μm are observed on the hole entrance using the four-layer diamond coated tools. Therefore, considering both the working life and holes quality, the MNMNCD films excel in the cutting performance of the new type of PCB drilling.