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With the aim to develop electrically conductive adhesives (ECAs) as alternatives for traditional lead-based or lead-free solders in electronic packaging, we report an outstanding enhancement of electrical conductivity of epoxy ECAs filled with silver nanoparticles (AgNP)-decorated graphene nanoplatelets (AgNP@GNP). In order to avoid the deterioration of the superior properties of GNP, the GNP is directly sensitized by Sn precursor without conventional harsh-conditioned graphene oxide (GO) preparation, followed by the decoration of AgNP on sensitized GNP. The structural and morphological properties of AgNP@GNP were characterized using XRD, TEM, Raman, and TGA. The excellent distribution of SnO2 and AgNP on GNP could be explained by the attractive force between protonated GNP (pH +20 mV) and lone-paired stannous ions. The electrical conductivity of as-prepared AgNP@GNP (1.3 × 105 S/cm) was nearly 6500 times than that of pristine GNP. Moreover, the electrical conductivity of the 20 vol% AgNP@GNP/epoxy ECAs was almost 500 times higher than that of pristine GNP/epoxy and 27-fold higher than that of conventional AgNP@GO/epoxy ECA.

Graphite exhibits electromagnetic wave attenuation and high electrical conductivity. In this study, we analyzed the electromagnetic interference shielding effectiveness (EMI SE) performance and electric conductivity of composites fabricated by varying the size (mean size: 6–100 µm) of graphite fillers and explained resulting attributes through the relative permittivity and geometrical characteristics of the filler. When the graphite/paraffine wax composite was fabricated using large-sized graphite (KS150), the spacing between the graphite fillers became widened, enabling electromagnetic waves to leak through the gap. The analysis results indicated that KS150 graphite exhibited an EMI SE performance of under 10 dB when the filler content was 30 wt%. However, when the content was increased to 50 wt%, the EMI SE performance improved sharply to 40 dB. In contrast, when the composite was filled with small-sized graphite (KS6), having a high ratio of surface to volume, the EMI SE performance was greater than that with the largesized graphite at low loading. The results related to the EMI shielding performance of graphite-filled composites revealed that the size of the filler greatly affects the EMI SE. The composite using KS75 showed an EMI SE performance of 53.0 dB and electrical conductivity of 2,000 S/m.

As environmental issues continuously increase, the development of effective and eco-friendly catalytic systems in organic chemistry is of great importance. To achieve this goal, two representative ...

This paper studies the trajectory planning problem for space robot system including two 7 degrees-of-freedom (DOFs) space manipulators. The base disturbance problem is not discussed. An intuitive close-form inverse-kinematic solution is first deduced to convert the Cartesian pose of end-effector into joint configurations. Two innovative functions, crawling function and cascade connection between Core Module Manipulator (CMM) and Experimental Module Manipulator (EMM) are studied and provided with mathematical solutions. Their purposes are to broaden the workspace while requiring higher demands on the planning method. Collision prediction including collision against the environment and against the robot itself is then analyzed to eliminate the tunneling problem and enhance efficiency. Finally, an improved trajectory planning method based on Lazy Theta* which is an algorithm of any-angle-path planning is proposed and adjusted to different planning conditions. Simulation results prove the comprehensive validity of this method. The collision-free trajectory is reasonable and optimized for shorter length and less turns. This method has preferable efficiency and utility to complex environment and changing free configuration space.

Uniform Pd nanoparticles immobilized on N-(3-trimethoxysilylpropyl)diethylenetriamine (PDETA)-functionalized fibrous silica KCC-1 (Pd/KCC-1-PDETA) were prepared with a mean Pd particle size of 2.8 nm. After characterization using powder X-ray diffraction, X-ray photoelectron spectroscopy, and N2 adsorption-desorption isotherms, Pd/KCC-1-PDETA was used as catalyst for additive-free dehydrogenation of formic acid to produce H2. Pd nanoparticle catalysts supported on two other mesoporous silica materials (MSF and KIT-6) were also synthesized to examine how the support affects the reaction. Among the three catalysts, Pd/KCC-1-PDETA exhibited significant catalytic activity (a turnover frequency of 332 h−1 at 323 K and 100% selectivity towards hydrogen), owing to the unique fibrous morphology of KCC-1 and the presence of amine groups that reduced the Pd particle size and improved the access of reactant to the catalytically active Pd sites. The influence of Pd loading (2–10 wt.%), reaction temperature, and reaction time was also examined for the dehydrogenation reaction. Pd/KCC-1-PDETA was recovered easily after the reaction and showed good reusability up to five times without any significant loss in catalytic performance.

Purpose This paper aims to purpose an improved sensorless position-based force controller in gravitational direction for applications including polishing, milling and deburring. Design/methodology/approach The first issue is the external force/torque estimation at end-effector. By using motor’s current information and Moore-Penrose generalized inverse matrix, it can be derived from the external torques of every joints for nonsingular cases. The second issue is the force control strategy which is based on position-based impedance control model. Two novel improvements were made to achieve a better performance. One is combination of impedance control and explicit force control. The other one is the real-time prediction of the surface’s shape allowing the controller adaptive to arbitrary surfaces. Findings The result of validation experiments indicates that the estimation of external force and prediction of surface’s shape are credible, and the position-based constant contact force controller in gravitational direction is functional. The accuracy of force tracking is adequate for targeted applications such as polishing, deburring and milling. Originality/value The value of this paper lies in three aspects which are sensorless external force estimation, the combination of impedance control and explicit force control and the independence of surface shape information achieved by real-time surface prediction.

Novel palladium complexes composed of palladium and a conjugated ligand (imine–aldehyde) were immobilized on graphene oxide. The developed catalyst was characterized by XPS, and TEM. The novel catalyst was proven to be highly efficient for the Suzuki-Miyaura coupling reaction of aryl halides (Br, Cl) with arylboronic acids under mild conditions with a low amount of catalyst (0.1 mol%). In particular, excellent yields could be also obtained at room temperature within 1 h for monosubstituted aryl bromide coupling. Furthermore, the novel catalyst could be reused at least ten times without significant loss of its catalytic activities.

Water pollution due to heavy metal ions from factories causes serious threats as the heavy metal ions are inclined to accumulate in living systems threat ening their health. Adsorption is considered one of the most promising wastewater purification techniques for its simple operation and high effectiveness compared with other techniques. Accordingly, a novel cost-effective and environmentally benign porous melamine-vanillin polymer (MVP) was synthesized via Schiff-base formation reaction, which was utilized for the removal of Pb(II) ions. The MVP achieved a high surface area of 745 m2 g-1 with a hierarchically porous structure consisting of 1 nm and 3–50 nm pores. Effects of the contact time and the initial heavy metal concentration on the adsorption of Pb(II) were studied. Due to the copious functional groups and the hierarchical pore size distribution, MVP was found to exhibit a good adsorption performance toward Pb(II) ions. The adsorption process was well-fitted to the Langmuir adsorption isotherm and the pseudo-1st-order kinetic model.

A practical heterogeneous catalyst was prepared by anchoring a triazine-tethered N-heterocyclic carbene (NHC)–palladium complex on the surface of graphene oxide (GO) nanosheets. The immobilized complex was characterized by X-ray photoelectron spectroscopy, field-emission transmission electron microscopy, energy-dispersive X-ray spectroscopy, and surface area analysis. It proved to be a highly active and durable heterogeneous catalyst for Suzuki coupling reactions. At room temperature, the use of this catalyst enabled the preparation of various biaryls and heterobiaryls in short reaction times. The catalytic system could be recycled at least 10 times with almost consistent activity. The results reveal that the stable palladium complex is strongly anchored on the surface of GO nanosheets. Interestingly, an open planar network of the GO nanosheet support plays a role during the catalytic process in enhancing the catalytic activity.

Over the past decade, advantages of graphene in high-performance gas sensing have been demonstrated, especially for single- or few-layered graphene wherein the theoretical and technical advances are mature. Owing to the complexity of multi-layered graphene (MLG) sensors and the increasing demand for practical applications, there is an urgent need to comprehensively understand the correlation between MLG and its derivatives for developing next-generation gas sensors. Herein, theoretical and empirical strategies for obtaining better gas sensors are developed. These approaches can be divided into three categories: 1) building devices with Fermi level near the Dirac point (EF,Dirac), 2) enhancing the adsorption probability f(x) and driving force (gap between as-prepared and saturated Fermi levels), and 3) accelerating mobility. A device employing p-type reduced graphene oxide (rGO) decorated with n-type indium oxide and phenylenediamine (GIP) was designed and fabricated by adopting approaches 1 and 2 (EF,Dirac and f(x) enhancement). The resulting hole-compensated GIP displayed a remarkable response to formaldehyde (HCHO), which was 66.3 times higher than rGO, with faster response/recovery. GIP also exhibited higher selectivity for HCHO than for ammonia and trimethylamine. We believe that the classification will untangle the complex role of graphene in sensing, helping to design next-generation advanced gas sensors.

Owing to the environmental and economic problems arising from fly ash (FA), there have been various ongoing efforts over the past decades to find a use for it. Among the various applications of FA, its use as a filler in polymer composites has gained much attention. However, most studies have applied FA as a semi-reinforcing filler, which only marginally improves mechanical properties arising from the poor surface wettability of FA with polymer matrices. To solve this problem and to explore new applications, FA was carbonated by bubbling CO2 in water in this study. The carbonated FA was adopted as a fire-proofing filler in silicone rubber (SR). The surface properties and compositional changes of FA by carbonation were thoroughly examined. Mechanical and thermal properties of carbonated FA-filled SR were evaluated. In particular, the gas torch test confirmed that the carbonation of FA increased the penetration time of SR composites by 11%. In addition, the penetration time of the carbonated FA-filled SR composite was 2–3 times greater than that of the composites filled with commercially available fillers.

Pollution emitted from power plants, including a considerable amount of fly ash (FA) and carbon dioxide (CO2), annually increases and is challenging from an environmentally friendly and sustainable point of view. To date, laboratory-scaled approaches cannot efficiently replace the FA-landfilling and mitigate the stress from CO2 emission. Here, a practically operatable fundamental work by combining carbonated FA (C-FA)—immobilizing CO2 in FA—and polypropylene (PP) matrix is reported and reveals abnormal mechanical and thermal features clarified by calculating van der Waals (vdW) interaction from an atomic scale. This is the first study wherein the interaction between instantaneous dipole moment-induced PP and fillers is simulated and examined. The vdW interactions at the (hetero)interfaces are –59.66, –82.30, and −224.39 kJ mol−1 A−2 for PP, calcium oxide (CaO; before carbonation), and calcium carbonate (CaCO3; after carbonation), respectively, which provides concrete theoretical support for interesting findings such as the independence of tensile strength on filler loadings and “well-grown” interface-induced higher conductivity characteristics of the composites. Therefore, this work can offer practical solutions to mitigate pollution, provide a new perspective on fundamental physical interactions, and guide the development of practical next-generation composite materials.

A series of highly microporous carbon materials was produced by carbonization of a triazine-based covalent organic polymer (TCOP) followed by carbonization and CO2 physical activation. The N-containing porous COP was prepared from easily available economic monomer precursors via a simple Friedel-Crafts reaction, which produced a predominantly microporous structure with a high surface area. Carbonization at 600–900 °C produced predominantly microporous carbons with a narrow pore size distribution in the range of 0.5–1.5 nm. Upon further activation using CO2, more micropores were formed, accompanied by an increase in the surface area (to 2003 m2 g−1) and the nitrogen level in the carbon structure was maintained at ca. 2 wt%. The electrochemical properties of the samples were measured by employing a three-electrode system with 6 M KOH electrolyte. Among the prepared carbon samples, the electrode fabricated using the carbon activated at 900 °C (AC-900) had a specific capacitance of 278 F g−1 at a current density of 1 A g−1, which is significantly higher than that of a commercial activated carbon (130 F g−1) and ranks among the highest reported so far. This improved performance was attributed to the highly microporous structure of the nitrogen-doped carbon with a narrow pore size distribution.

In this paper, a novel human direct teaching method of industrial manipulator with large mass and friction based on internal current sensors installed in joints is proposed. Dynamic model for an industrial robot is analyzed in detail, where the gravity torque and friction torque are the main items that need to be considered. Friction torque is influenced by joint speed and temperature. A method to identify joint friction parameters rapidly is proposed, and experiments are carried out to acquire friction characteristics under different temperatures. Then, the implementation method and improvement measures of direct human teaching are introduced in consideration of robot gravity torque and friction torque of joints. Finally, validation tests are conducted to verify the feasibility of the direct teaching method. Experiment result shows that the method based on internal current sensors is capable of realizing direct teaching flexibly and easily.

Ceramic coatings endow carbon materials with electrically insulating properties. For graphite, it is unclear whether ceramic coatings applied via a one-step process under mild conditions can lead to superior coverage. This paper reports that a modified Stober method with an appropriate choice of amphiphiles could yield an electrically insulating coating layer on graphite (d50 3–300 μm, d90 6–550 μm) within 24 h with high reproducibility. A silica coating mechanism involving functional groups on the edge of the graphite, Oswald ripening agents, and a bridgemer was investigated. The mechanism was based on the silica coating morphology, which depends on the amphiphile, and the correlation between coverage and surface resistivity was assessed. Amphiphile-assisted silica@graphite with a surface resistivity of 1012 ohm sq−1 was produced. The thermal conductivity of the silica-coated graphite (amphiphile-assisted silica@graphite)/TPEE composite reached values over 75% higher than that of the raw graphite/TPEE composite with electrically insulating properties.

Porous organic polymers (POPs) with well-distributed and tunable functional groups acting as ligands for specific reactions are promising supports for confining useful novel metals such as Pd, Au, and Pd. Herein, a thiadiazole-containing POP has been successfully synthesized and used for immobilizing Pd species. Pd immobilized inside the micropores (2.3 nm) of the POP material is easily prepared owing to a large amount of the strong anchoring group, thiadiazole, which is intrinsically distributed in the as-prepared POP. The rigid thiadiazole-containing polymer can stabilize the central metal rather than poisoning it. The as-prepared catalyst shows excellent catalytic activity in Suzuki–Miyaura coupling reactions under mild reaction conditions and low catalyst loading. Importantly, the intrinsically distributed thiadiazole ligands can stabilize the Pd moiety, preventing aggregation and leaching, and afford excellent catalytic lifetimes. Consequently, the catalyst can be reused 10 times without a significant loss of its catalytic activity.

For a graph H, let c ∞ ( H ) = lim n → ∞ ⁡ max ⁡ | E ( G ) | n , where the maximum is taken over all graphs G on n vertices not containing H as a minor. Thus c ∞ ( H ) is the asymptotic maximum density of graphs not containing H as a minor. Employing a structural lemma due to Eppstein, we prove new upper bounds on c ∞ ( H ) for disconnected graphs H. In particular, we determine c ∞ ( H ) whenever H is a union of cycles. Finally, we investigate the behaviour of c ∞ ( s K r ) for fixed r, where s K r denotes the union of s disjoint copies of the complete graph on r vertices. Improving on a result of Thomason, we show that c ∞ ( s K r ) = s ( r − 1 ) − 1 for s = ω ( log ⁡ r log ⁡ log ⁡ r ) , and c ∞ ( s K r ) > s ( r − 1 ) − 1 for s = o ( log ⁡ r log ⁡ log ⁡ r ) .

Graphene oxide (GO) was functionalized with a series of amine precursors including ammonia, methylamine, ethylamine, ethylenediamine, dimethylamine, aniline, and 1,4-phenylenediamine (PDA) by a facile solvothermal method for room temperature formaldehyde (HCHO) gas sensing. The as-prepared materials were fabricated via a simple drop-casting method and screened based on the response to 300 ppm HCHO gas at room temperature. GO functionalized with 1,4-phenylenediamine (PDA-GO) was the most sensitive toward 300 ppm HCHO compared to combinations of GO with other amines. The PDA-GO was characterized by transmission electron microscopy, scanning electron microscopy, Raman spectroscopy, Fourier transform infrared spectrometer, and X-ray photoelectron spectroscopy to investigate the morphology and chemical structure. Remarkably, the response of PDA-GO was almost 24 times higher than that of GO and reached up to 24%. The excellent HCHO sensing properties of the PDA-GO sensor were elucidated by DFT study, which are attributed to the harmony of strong bond formation energy, adsorption energy, and charge transfer during the PDA-GO physically interacting with HCHO. Compared with other reported graphene-based room temperature HCHO gas sensors, PDA-GO exhibits great potential and represents a contribution to the limited studies in the field of organic molecule-functionalized graphene derivatives for HCHO sensor applications.

An efficient porous organic polymer (POP)-based adsorbent (4AS-MBP), synthesized from melamine, 4-allyloxy benzaldehyde and ethanedithiol (EDT) via a Schiff-base reaction and thiol–ene addition in a straightforward strategy, was prepared to remove Hg(II) ions from water. The chemical structure and morphology of 4AS-MBP were investigated by FT-IR, solid-state 13C NMR, EA, SEM, TEM and BET analysis. Adsorption experiments were conducted by varying the Hg(II) concentration, contact time and pH to study the adsorption kinetics and equilibrium. Mesoporous 4AS-MBP exhibited a maximum adsorption capacity of 312 mg g−1. The results indicated that Hg(II) adsorbed onto the adsorbent through monolayer chemisorption. Interestingly, 4AS-MBP was highly stable, even in the presence of 2 M NaOH or HCl, and displayed similar adsorption capacities over a wide pH range. Furthermore, the adsorbents could be reused at least five times without a loss of adsorption capacity. More importantly, the relative selectivity coefficients of 4AS-MBP for Hg()/Pb(II), Hg(II)/Cd(II), Hg(II)/Cu(II), Hg(II)/Zn(II) and Hg(II)/Mg(II) were 54.3, 221, 243, 468 and 823, respectively.

This study aims to explore the application of storyboard and combination of storyboard and the technology of Internet of things (IoT) into the vehicle interactive design to improve deaf drivers’ experience. To achieve the aim, we introduced the storyboard approach into user need study and product prototype design, and practiced in the course of user experience at Beijing Union University. Our results show that the method has two benefits for students: 1. They can utilize storyboard to quickly understand the usage context of products without knowing the whole producing processes in real setting. 2. They can form future insights on the introduction of IoT into the vehicle interactive design, the deaf driving system, which has not been developed yet. This paper presents the approach in detail.

We introduce a simple method for proving lower bounds for the size of the smallest percolating set in a certain graph bootstrap process. We apply this method to obtain recursive formulas for the sizes of the smallest percolating sets in multidimensional tori and multidimensional grids (in particular hypercubes). The former answers a question of Morrison and Noel [9] , and the latter provides an alternative and simpler proof for one of their main results.

A β-diketiminatophosphane-palladium complex was found to act as an efficient and general catalyst in the Stille coupling reaction of various aryl and heteroaryl chlorides with organostannanes. The results show that this catalytic system allows for the use of less reactive substrates such as deactivated or sterically hindered aryl chlorides. A catalyst loading of 0.5 mol% was sufficient to achieve excellent performance under relatively mild reaction conditions. Furthermore, the scope of catalyst was extended to the coupling of vinyl chlorides.

A critical set in an $n \times n$ Latin square is a minimal set of entries that uniquely identifies it among all Latin squares of the same size. It is conjectured by Nelder in 1979, and later independently by Mahmoodian, and Bate and van Rees that the size of the smallest critical set is $\lfloor n^2/4\rfloor$. We prove a lower-bound of $n^2/10^4$ for sufficiently large $n$, and thus confirm the quadratic order predicted by the conjecture. We prove a lower-bound of $n^2/10^4$ for sufficiently large $n$, and thus confirm the quadratic order predicted by the conjecture. This improves a recent lower-bound of $\Omega(n^{3/2})$ due to Cavenagh and Ramadurai. From the point of view of computational learning theory, the size of the smallest critical set corresponds to the minimum teaching dimension of the set of Latin squares. We study two related notions of dimension from learning theory. We prove a lower-bound of $n^2-(e+o(1))n^{5/3}$ for both of the VC-dimension and the recursive teaching dimension., Comment: 12 pages, final version, to appear in Journal of Combinatorics

A T-cell receptor mimic peptide (TCRpep) consisting of an 8-amino-acid peptide, homologous to the transmembrane region of the T-cell receptor (TCR) alpha chain, blocks T-cell activation after systemic application. When dendritic cells (DCs) were transduced to secrete the TCRpep and injected into mice, evidence of immunosuppression was observed. In a CD8-driven allergy model, the injection of DCs transduced with the TCRpep reduced inflammation markedly and in a CD4+ T cell-dependent model of multiple sclerosis (experimental autoimmune encephalitis, EAE), injection of TCRpep-secreting DCs abrogated EAE symptoms and prolonged survival. These effects were antigen specific, because transduced DCs that did not express the respective antigen failed to convey protection in the allergy model as well as in the EAE model. Thus these data show that DCs expressing the TCRpep are able to suppress T-cell activation and might be a useful tool for inducing antigen-specific immune suppression in vivo.

Coupling of ovalbumin (OVA) to anti–DEC-205 monoclonal antibody (mAb) (αDEC) induced the proliferation of OVA-specific T cells in vivo. Expansion was short-lived, caused by dendritic cells (DCs), and rendered T cells anergic thereafter. Phenotypic analysis revealed the induction of CD25+/CTLA-4+ T cells suppressing proliferation and interleukin-2 (IL-2) production of effector CD4+ T cells. The findings were supported by 2 disease models: (1) CD4+ T-cell–mediated hypersensitivity reactions were suppressed by the injection of αDEC-OVA and (2) the application of hapten-coupled αDEC-205 reduced CD8+ T-cell–mediated allergic reactions. Thus, targeting of antigens to immature DCs through αDEC antibodies led to the induction of regulatory T cells, providing the basis for novel strategies to induce regulatory T cells in vivo.

The use of the highly active catalyst PPA renders possible the coupling of deactivated or sterically hindered aryl chlorides and vinyl chlorides with organostannanes to provide a variety of coupling products (44 examples).

Targeting of antigens to immature dendritic cells has been shown to result in antigen-specific T-cell tolerance in vivo. In the INS-HA/TCR-HA transgenic mouse model for type 1 diabetes, we tested the potential of the dendritic cell-specific monoclonal antibody DEC-205 conjugated to the hemagglutinin (HA) antigen (DEC-HA) to prevent disease onset. Whereas untreated INS-HA/TCR-HA mice all develop insulitis, and approximately 40% of these mice become diabetic, repeated injection of newborn mice with DEC-HA protected almost all mice from disease development. Histological examination of the pancreata revealed significant reduction of peri-islet infiltrations in DEC-HA-treated mice, and the islet structure remained intact. Moreover, HA-specific CD4+ T-cells from anti-DEC-HA-treated INS-HA/TCR-HA mice exhibited increased expression of Foxp3, cytotoxic T-lymphocyte-associated antigen-4, and the immunosuppressive cytokines interleukin-10 and transforming growth factor-beta. The findings indicate that targeting of the HA antigen to immature dendritic cells in vivo leads to a relative increase of antigen-specific Foxp3+ regulatory T-cells that suppress the development of type 1 diabetes. Our results provide a basis for the development of novel strategies focusing on prevention rather than treatment of autoimmune diseases.