When connected piles are used as settlement reducers, the proportion of vertical load carried by the pile may come close to the allowable load of the pile. To reduce not only the vertical load, but ...also the lateral load and bending moment to which the pile is subjected, the disconnected piled raft (DPR) has been introduced as an effective design for the role of the settlement reducers. Although several DPRs have been constructed, most of the research efforts on DPRs are limited to the structural behavior such as the evaluation of the seismic acceleration of the structure on the DPR; thus, there is a need to evaluate the dynamic performance of DPRs focusing on geotechnical problems. In this study, the seismic behavior of DPRs is investigated using dynamic centrifuge tests and compared with the results obtained from connected piled rafts (CPRs). The bending moment of piles of different materials, namely aluminum and steel, is evaluated. Results show that there is a reduction in the amplitude of acceleration of the foundation horizontal motion for the DPR compared to the CPR. The edge pile of a DPR attracts the smaller dynamic bending moment of the pile compared to that of a CPR. The dynamic bending moment of piles is predominantly governed by the soil behavior rather than the pile material. Finally, the seismic behavior of DPR was evaluated comprehensively through centrifuge tests.
A disconnected piled raft (DPR) foundation has been introduced as an effective pile design to reduce the vertical loading experienced by the pile. The characterization of DPRs has focused on the load ...transfer mechanism, foundation and soil settlement, bearing capacity, load distribution, and bending moment of the piles. DPR piles can act to increase the bearing capacity of the ground, and DPRs can reduce settlement while securing the bearing capacity. In this study, centrifuge model tests are performed to simulate the static behavior of DPRs under actual stress conditions. The behaviors of the DPR foundation for axial load, axial load distribution among the piles, and bending moment are compared to those of the connected piled raft foundation to understand the complex behaviors of DPRs. The centrifuge test results show that DPRs help reduce the pile axial load and bending moment during vertical loading. In addition, DPRs show smaller vertical settlement than shallow foundations. Therefore, we confirm that DPRs can be applied in foundation design as settlement reducers.
Poly（3-hexylthiophene） （P3HT） has received much attention as a good candidate to replace inorganic semiconductors for flexible electronics due to its solution-processability. However, the low charge ...mobility of P3HT is an obstacle to its commercialization. To overcome this problem, we propose a new non-covalent functionalization method for carbon nanotubes （CNTs） for use in CNT/P3HT nanocomposites. By using modified pyrene molecules with hydrophobic long alkyl chains, the non-covalently functionalized CNTs can become well dispersed in hydrophobic solutions and organic semiconductor matrices. Fabrication of organic thin-film transistors （OTFTs） from the non-covalently functionalized CNT/organic semiconductor nanocomposites shows that our non-covalent functionalization method significantly reduces damage to CNTs during functionalization when compared with covalent functionalization by treatment with acids. The OTFTs show 15 times enhancement of field effect mobility （1.5 × 10^-2 cm^2/（V.s）） compared to the mobility of OTFTs made from pure P3HT. This enhancement is achieved by addition of only 0.25 wt% of CNTs to P3HT.
The band gap properties of graphene quantum dots (GQDs) arise from quantum confinement effects and differ from those in semimetallic graphene sheets. Tailoring the size of the band gap and ...understanding the band gap tuning mechanism are essential for the applications of GQDs in opto-electronics. In this study, we observe that the photoluminescence (PL) of the GQDs shifts due to charge transfers between functional groups and GQDs. GQDs that are functionalized with amine groups and are 1–3 layers thick and less than 5 nm in diameter were successfully fabricated using a two-step cutting process from graphene oxides (GOs). The functionalized GQDs exhibit a redshift of PL emission (ca. 30 nm) compared to the unfunctionalized GQDs. Furthermore, the PL emissions of the GQDs and the amine-functionalized GQDs were also shifted by changes in the pH due to the protonation or deprotonation of the functional groups. The PL shifts resulted from charge transfers between the functional groups and GQDs, which can tune the band gap of the GQDs. Calculations from density functional theory (DFT) are in good agreement with our proposed mechanism for band gap tuning in the GQDs through the use of functionalization.
The scalable preparation of two-dimensional hexagonal boron nitride (h-BN) is essential for practical applications. Despite intense research in this area, high-yield production of two-dimensional ...h-BN with large-size and high solubility remains a key challenge. In the present work, we propose a scalable exfoliation process for hydroxyl-functionalized BN nanoplatelets (OH-BNNPs) by a simple ball milling of BN powders in the presence of sodium hydroxide via the synergetic effect of chemical peeling and mechanical shear forces. The hydroxide-assisted ball milling process results in relatively large flakes with an average size of 1.5 μm with little damage to the in-plane structure of the OH-BNNP and high yields of 18%. The resultant OH-BNNP samples can be redispersed in various solvents and form stable dispersions that can be used for multiple purposes. The incorporation of the BNNPs into the polyethylene matrix effectively enhanced the barrier properties of the polyethylene due to increased tortuosity of the diffusion path of the gas molecules. Hydroxide-assisted ball milling process can thus provide simple and efficient approaches to scalable preparation of large-size and highly soluble BNNPs. Moreover, this exfoliation process is not only easily scalable but also applicable to other layered materials.
The demand for wearable strain gauges that can detect dynamic human motions is growing in the area of healthcare technology. However, the realization of efficient sensing materials for effective ...detection of human motions in daily life is technically challenging due to the absence of the optimally designed electrode. Here, we propose a novel concept for overcoming the intrinsic limits of conventional strain sensors based on planar electrodes by developing highly periodic and three-dimensional (3D) bicontinuous nanoporous electrodes. We create a 3D bicontinuous nanoporous electrode by constructing conductive percolation networks along the surface of porous 3D nanostructured poly(dimethylsiloxane) with single-walled carbon nanotubes. The 3D structural platform allows fabrication of a strain sensor with robust properties such as a gauge factor of up to 134 at a tensile strain of 40%, a widened detection range of up to 160%, and a cyclic property of over 1000 cycles. Collectively, this study provides new design opportunities for a highly efficient sensing system that finely captures human motions, including phonations and joint movements.
Long‐lived afterglow emissions, such as room‐temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF), are beneficial in the fields of displays, bioimaging, and data ...security. However, it is challenging to realize a single material that simultaneously exhibits both RTP and TADF properties with their relative strengths varied in a controlled manner. Herein, a new design approach is reported to control singlet–triplet energy splitting (∆EST) in graphene quantum dots (GQD)/graphene oxide quantum dots (GOQDs) by varying the ratio of oxygenated carbon to sp2 carbon (γOC). It is demonstrated that ∆EST decreases from 0.365 to 0.123 eV as γOC increases from 4.63% to 59.6%, which in turn induces a dramatic transition from RTP to TADF. Matrix‐assisted stabilization of triplet excited states provides ultralong lifetimes to both RTP and TADF. Embedded in boron oxynitride, the low oxidized (4.63%) GQD exhibits an RTP lifetime (τTavg) of 783 ms, and the highly oxidized (59.6%) GOQD exhibits a TADF lifetime (τDFavg) of 125 ms. Furthermore, the long‐lived RTP and TADF materials enable the first demonstration of anticounterfeiting and multilevel information security using GQD. These results will open up a new approach to the engineering of singlet–triplet splitting in GQD for controlled realization of smart multimodal afterglow materials.
Oxidation control of graphene quantum dots can tune the singlet–triplet energy splitting, which induces a dramatic afterglow transition from phosphorescence to thermally activated delayed fluorescence. Matrix‐assisted stabilization of triplet excited states provides ultralong lifetimes to such afterglow emissions. A new design approach for engineering singlet–triplet energy splitting through facile molecular manipulation will enable the realization of smart multimodal afterglow materials.
Graphene quantum dot (GQD) light‐emitting diodes (GQD‐LEDs) are shown to have an electroluminescence exceeding 1000 cd m‐2. These devices are possible due to a novel synthesis method to create GQDs ...with minimal oxidation, guaranteeing high quantum yields via the solvothermal formation of graphite intercalation compounds between graphite powder and sodium potassium tartrate. The GQDs are incorporated into polymeric host layers in a multilayer device and irradiate blue (~400 nm) emission.
Atopic dermatitis (AD) is a common chronic inflammatory skin disease. Interleukin 31 (IL-31), a novel cytokine in AD, causes pruritus, typically characteristic of AD patients. The transient receptor ...potential vanilloid type 1 (TRPV1) is a cation channel activated by diverse noxious stimuli that has been studied in a variety of pruritic skin diseases. In this study, the AD animal model was generated by administering the hapten, trinitrochlorobenzene (TNCB), to Nc/Nga mice, and the degree of expression of the IL-31 receptor alpha (IL-31RA) and TRPV1 in the skin of these atopic models was evaluated. The Nc/Nga mice were divided into 3 groups: control, TNCB 2-weeks treated, and TNCB 8-weeks treated. After inducing AD, the skin lesions in each group were scored and compared, and the histology of the skin lesions and the IL-31RA and TRPV1 expression for each group were evaluated by analyzing immunohistochemistry. The results show a significant difference in the skin lesion scores between the groups. The immunohistochemistry evaluation highlighted the remarkable expression of IL-31RA and TRPV1 in the nerve fibers of the TNCB 8-weeks-treated group. We thus confirmed that the long-term application of TNCB induced chronic atopic-like dermatitis and that IL-31RA and TRPV1 were overexpressed in the peripheral nerve fibers in this AD model.
The influence of surface modifications on the mechanical properties of epoxy‐hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. Homogeneous distributions of boron nitride ...nanoflakes in a polymer matrix, preserving intrinsic material properties of boron nitride nanoflakes, is the key to successful composite applications. Here, a method is suggested to obtain noncovalently functionalized BNNFs with 1‐pyrenebutyric acid (PBA) molecules and to synthesize epoxy–BNNF nanocomposites with enhanced mechanical properties. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields an elastic modulus of 3.34 GPa, and 71.9 MPa ultimate tensile strength at 0.3 wt%. The toughening enhancement is as high as 107% compared to the value of neat epoxy. The creep strain and the creep compliance of the noncovalently functionalized BNNF nanocomposite is significantly less than the neat epoxy and the nonfunctionalized BNNF nanocomposite. Noncovalent functionalization of BNNFs is effective to increase mechanical properties by strong affinity between the fillers and the matrix.
The influence of surface modifications on the mechanical properties of epoxy‐hexagonal boron nitride nanoflake (BNNF) nanocomposites is investigated. The BNNFs chemically surface modified by noncovalent functionalization are prohibited from stacking and aggregation, resulted in homogeneous dispersions in the epoxy matrix with strong interfacial interactions. The incorporation of noncovalently functionalized BNNFs into epoxy resin yields outstanding strength and toughness at low BNNF loadings.
