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A series of tailor-made highly efficient and near-infrared (NIR) porphyrin-based acceptors is designed and synthesized for fullerene-free bulk-heterojunction (BHJ) organic solar cells. Constructing BHJ active layers using a PTB7-Th donor and porphyrin acceptors (P-x), which have complementary absorption, accomplishes panchromatic photon-to-current conversion from 300 to 950 nm. Our study shows that side chains of the porphyrin acceptors fairly influence the molecular ordering and nanomorphology of the BHJ active layers. Significantly, the porphyrin acceptor with four dodecoxyl side chains (P-2) achieves an open-circuit voltage (VOC) of 0.80 V, short-circuit current density (JSC) of 13.94 mA cm-2, fill factor of 64.8%, and overall power conversion efficiency of 7.23%. This great performance is attributable to the ascendant light-harvesting capability in the visible and near-infrared region, a high-lying LUMO energy level, a relatively high and more balanced carrier mobilities, and more ordered face-on molecular packing, which is beneficial for obtaining high VOC and JSC.

Wi-Fi was developed to support software-defined networks that are crucial for achieving high quality of service for next generation wireless networks. In this software-defined networking technology, network resources are utilized to reduce the effects of several influential factors such as the limited number of nonoverlapping channels, co-channel interference, rapidly changing distribution of customers, and access point (AP) failure. These factors cause irregular network traffic and service unavailability in some users. In this paper, we address the problems causing the AP failure and interference. The studied problems were modeled as linear and nonlinear mathematical programming problems. The Lagrangian relaxation approach, which is a type of divide-and-conquer method, was used to solve the load distribution problems near optimally. A self-repairing heuristic multiple-level load-balancing traffic adjustment was proposed to manage the problems pertaining to the AP failure. The delay difference metric, which is defined as the difference between tolerable delay and transmission delay, was used to evaluate the difference between the upper bound and lower bound of the delay. Moreover, the metric was used to estimate the improvement ratio between the existing methods and the proposed method. Modifiable transmission power ranges (which involve the cell breathing method) and association managements are adjusted to minimize the narrow gap and improve the self-repairing performance. Thus, resources are appropriately allocated to users, and adequate QoS is attained.

The outbreak of COVID-19 around the world has caused great damage to the global economy. The tourism industry is among the worst-hit industries. How to focus on visitors who are most helpful to the tourism industry and develop sustainable strategy of operation is a very important question for after the epidemic is over. This study applied two-stage data envelopment analysis (DEA) and principal component analysis (PCA) to investigate past statistics from the Tourism Bureau and explore the shopping patterns of tourists who travel to Taiwan. The focus will be on tourists from major countries such as China, Japan, and Southeast Asian countries. According to the analysis of tourists from different countries, the money spent by tourists from different countries is concentrated on different items, and there are subitems that they particularly like to purchase. For the analysis of the purpose of coming to Taiwan, some tourism areas worth developing (such as medical treatment and leisure) are also presented in the research results. Based on these results, and according to the sustainable development goals, specific recommendations for the sustainability strategy of operation are made as a reference for the government and relevant industries. This research also broadens the scope of application of DEA and points out a different direction for future research.

Four pyrene-porphyrins were synthesized to study the isomer effect on the photovoltaic performance of dye-sensitized solar cells. One of these porphyrins is conjugated with a terminal pyrene, whereas the other three are each attached with a pyrene bearing an extra donor group. According to the positions of the extra donor and porphyrin core on pyrene, the 1,6-, 1,8-, and 2,7-isomers were compared for their fundamental and photovoltaic properties. For fundamental properties, UV-visible absorption, fluorescence emission, electrochemistry, and DFT calculations were carried out. For photovoltaic measurements, the seemingly inferior 1,8-isomer outperforms others with an overall efficiency of 10.30% under one-sun irradiation. Superior photovoltaic performance of the 1,8-isomeric dye may be related to the so-called umbrella effect. The findings of this work may provide insight into isomeric dye design for future applications.

Since Charnes, Cooper, and Rhodes introduced data envelopment analysis (DEA) in 1978, later called the DEA-CCR model, many studies applied this technique to different fields. Based on the original CCR model, many modified DEA models were developed by researchers. Since 1999, Seiford and Zhu presented a two-stage DEA model. Later, these models were widely used in many studies. However, the relationship between the efficiency scores that are obtained from the original CCR model and the two-stage DEA model remains unknown. To fill this gap, this study proposed a theoretical relationship between the efficiency scores that are calculated from the two-stage DEA model and those that are obtained from the original CCR model. How the sets of nonsymmetrical weights affected the efficiency scores were also investigated. Theorems regarding the relationship were developed, and then the model was utilized to evaluate the two-stage efficiency scores of the insurance companies (non-life) and bank branches. The results show that using a two-stage DEA model can get more information about operational efficiency than the traditional CCR model does. The findings from this study about the two-stage DEA technique can provide significant reasons for using this model to evaluate performance efficiency.

Three novel anthracene-based organic dyes, denoted as AN-11, AN-12 and AN-14, were synthesized for outdoor and indoor dye-sensitized solar cell studies. Laboratory-fabricated small cells, as well as rigid and flexible modules, were prepared and analyzed for their photovoltaic performance under simulated outdoor and indoor conditions. Owing to the panchromatic absorption of visible light, the AN-11 module gives rise to a very black color and superior photovoltaic performance. Significantly, the AN-11 rigid module with a large active area of 26.80 cm2 outperforms its Z907 counterpart under indoor conditions, reaching an overall efficiency of 11.94% under 1000 lux of T5 fluorescent light. In addition, the AN-11 module exhibits good stability during weather stress tests. Finally, the AN-11 dye is cost-effective and our studies show that the photovoltaic performance of the solar cells is not affected upon lowering the synthetic cost and increasing the synthetic scale.

In this study, the high-crystallinity vertical platinum nanosheets (PtNSs) were deposited onto the carbon nanotubes (CNTs) directly grown on the carbon paper (CP) as the PtNSs/CNTs/CP hybrid nanostructure to promote the electrocatlytic performance of methanol oxidation reaction (MOR). CNTs were initially synthesized on the carbon fibers of CP as catalyst supporting material by chemical vapor deposition method. Subsequently, PtNSs electrocatalysts with high activity were synthesized onto the CNTs surface by electrodeposition method. Scanning electron microscopy, high-resolution transmission electron microscopy and X-ray diffraction were employed to investrage the morphology and structural features of PtNSs/CNTs/CP. The Pt loading was examined by inductively coupled plasma mass spectrometry. The electronic structures of PtNSs were examined by X-ray photoelectron spectroscopy. The electrocatalytic properties were examined by Cyclic Voltammetry method. Our work suggests that PtNSs/CNTs/CP electrode could provide higher surface area with a lower Pt content and show better crystalline than Pt Black. The catalytic efficiency of prepared PtNSs/CNTs/CP electrode, as determined by the electrochemical active surface area and the catalyst mass activity for the MOR, were 1.39 times and 2.95 times better than those of a commercial Pt-black catalyst, suggesting that PtNSs/CNTs/CP electrode might be a good candidate for catalyst of MOR.

In this study, we controlled the growth of crystalline plane to synthesize the vertical platinum nanopelts onto fluorine doped tin oxide (FTO) glass to construct the platinum nanoroses (PtNRs) by an easy electrochemical deposition (ECD) method at room temperature in the normal atmospheric environment, and applied the PtNRs as a counter electrode (CE) for dye-sensitized solar cell (DSSC). The morphologies and crystalline nanostructures of the ECD PtNRs were examined by field emission scanning electron microscopy and the high-resolution transmission electron microscopy. The electrocatalytic properties of the ECD PtNRs were analyzed by cyclic voltammetry and electrochemical impedance spectrum. The power conversion efficiency (PCE) of the DSSC assembled with the ECD PtNRs CE was examined under the illumination of AM 1.5 (100 mWcm − 2 ). The ECD PtNRs showed well contact behavior with FTO surface and offered a large surface area to promote the redox reaction rates therefore increased the exchange current density. Due to the PtNRs showed the macroporous structure, the electrolyte can easily diffuse through the open space between the nanopelts, resulting in improved kinetics for charge-transfer processes and reduced the charge-transfer resistance. Our findings suggest that the catalytic efficiency of PtNRs with a specific crystal plane was significantly greater than that of a traditional Pt film catalyst. In combination with a N719 dye-sensitized TiO 2 working electrode and an iodine-based electrolyte, the DSSC assembled with the PtNRs CE achieved a PCE of 6.58%, almost 10% higher than that of a cell prepared with a conventional sputtering Pt film CE (6.00%). These results provide a potential strategy for electrochemical catalytic applications.

In this work, the coaxial nanostructure of ruthenium oxide (RuO x ) thin films coated onto the surface of the vertical graphitic nanofibers (GNFs) was developed and employed as electrodes for electrochemical supercapacitor. The vertically aligned GNFs were directly grown on the fluorine doped tin oxide glass via the chemical vapor deposition, and the RuO x thin films were prepared by an easy cyclic voltammetric electrochemical deposition. The morphologies and nanostructures of the coaxial-nanostructure RuO x /GNFs were investigated by the field emission gun scanning electron microscopy and the high-resolution transmission electron microscopy, respectively. Raman spectrum was used to examine the characteristic features of the RuO x /GNFs. The electrochemical properties were examined by cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectra. The directly grown GNFs not only played the attractive template that offered a large surface area to promote the loading of RuO x for enhancing electrochemical activity, but also provided a high-speed pathway that promoted charge transport and transfer. The macroporous structure of the vertically coaxial-nanostructure RuO x /GNFs avoided the self-aggregation, thus allowed the electrolyte can easily diffuse through the open space between them to enhance the electrochemical performance. The electrochemical measurements revealed that the excellent charge storage properties of the RuO x /GNFs can be obtained, the good electrochemical performance was attributed to the unique macroporous structure and the coaxial nanostructure of RuO x /GNFs.

In this report, vertically aligned one-dimensional (1D) cobalt sulfide nanoneedles (CS-NNs) were directly synthesized onto the three-dimensional graphene (3DG) as the CS-NNs/3DG hybrid nanostructure and applied to methanol oxidation reaction (MOR). The 3DG and CS-NNs were prepared by chemical vapor deposition and two-step hydrothermal method, respectively. The 1D cobalt carbonate hydroxide nanoneedles (CCH-NNs) were initially synthesized onto the graphene surface of 3DG via the hydrothermal method (Step I). Finally, the CCH-NNs were converted into CS-NNs via the hydrothermal treatment using Na 2 S as the sulfur source with the help of the Kirkendall effect (Step II). The structures and morphologies of 3DG, CCH-NNs/3DG, and CS-NNs/3DG were investigated by Raman spectroscopy, scanning electron microscopy and X-ray diffraction. The electrocatalytic performance was investigated by cyclic voltammetry measurements. The CS-NNs/3DG electrode showed higher electrocatalytic activity for MOR compared with CCH-NNs/3DG and 3DG. The excellent electrocatalytic performances of 3DG supported CS-NNs come from the unique 3D porous architecture, which can provide sufficient open spaces and shorter ion diffusion paths to facilitate rapid ionic transportation. Direct synthesis of 1D CS-NNs on graphene can result in a low resistance for fast electron transfer. The vertically aligned binder-free 1D CS-NNs not only avoid the aggregation to enhance the utilization efficiency of catalytic active sites but also serve as an electron highway in the axial direction for electron collection. The prepared CS-NNs/3DG is a promising non-platinum electrocatalyst for direct methanol fuel cells.

We herein report the synthesis, UV–vis absorption, fluorescence emission, and redox properties of three novel meso-diphenylbacteriochlorins. Significantly, we show that substituents at the meso-positions of an air-stable bacteriochlorin can be manipulated for the first time. With proper design, this allows tailor-made bacteriochlorins to exhibit suitable properties for a chosen application. As an example, photovoltaic properties of two such bacteriochlorins in dye-sensitized solar cells are investigated. The results show that the bacteriochlorin dyes outperform a reference porphyrin dye. Intriguingly, the anodes sensitized with the new dyes display rare colors—blue and pink.

This study proposes synthesizing high strength polyester (HSPET) fibers and polypropylene (PP) fibers to form HSPET/PP-fasciated yarns, which are tested for tensile strength after they are exposed to UV radiations. The yarns are then made into geogrids, after which the geogrids are tested by administering the single or multi-rib tensile method, and are then evaluated for mass per unit area and installation damage. The test results show that the tensile strength and elongation of the fascinated yarns decrease as a result of their exposure to UV. The geogrids that are composed of fascinated yarns are unable to evenly distribute a force. The installation damage of HSPET/PP geogrids is greater than that of traditional geogrids, as are the cases of other applications. As a result, HSPET/PP geogrids can be reformed to improve their inferior performances.

A new class of porphyrin-containing polyimides, ZnPor-s-DSDA, ZnPor-t-DSDA, Por-s-DSDA and Por-t-DSDA, were synthesized from porphyrin-containing diamines and 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride for resistor-type memory applications. The effect of the linkage and zinc metal was investigated by electrochemistry, molecular simulations, and memory behaviors. The memory devices with different retention times derived from polymers ZnPor-s-DSDA (WORM, >3 h) and ZnPor-t-DSDA (DRAM, 30 s) demonstrated the importance of the linkage effect, and the insulation property of polyimides Por-s-DSDA and Por-t-DSDA also implies a crucial memory behavior by metal chelation.

We design a novel solution-processable polyimide ZnPor-t-DSDA with porphyrin moiety (electron donor) and sulfone-containing phthalimide (electron acceptor) for polymer memory applications. The resulting memory device can be switched from low-conductivity (OFF) to high-conductivity (ON) by both positive and negative sweeps, exhibiting symmetry biswitching characteristic with a short retention time (30 s). On the basis of the simulation calculation, the coplanar structure between donor and acceptor units results in charge transferring easily back to its original state after being excited by an electric field.

Many different time-series methods have been widely used in forecast stock prices for earning a profit. However, there are still some problems in the previous time series models. To overcome the problems, this paper proposes a hybrid time-series model based on a feature selection method for forecasting the leading industry stock prices. In the proposed model, stepwise regression is first adopted, and multivariate adaptive regression splines and kernel ridge regression are then used to select the key features. Second, this study constructs the forecasting model by a genetic algorithm to optimize the parameters of support vector regression. To evaluate the forecasting performance of the proposed models, this study collects five leading enterprise datasets in different industries from 2003 to 2012. The collected stock prices are employed to verify the proposed model under accuracy. The results show that proposed model is better accuracy than the other listed models, and provide persuasive investment guidance to investors.

Wi-Fi wireless communication has become a basic service in public areas. However, the quality of service (QoS) might be inadequate in some areas because of the following influential factors: 1) the limited number of non-overlapping channels, 2) the interference caused by unplanned deployment and mobility, 3) the rapidly changing distribution of customers, and 4) access point (AP) failures. These factors result in non-uniform network traffic distribution and unavailability of service in some areas. Hence, this study focused on addressing the problems of AP failure and interference. We propose a self-healing algorithm to provide seamless and reliable service despite AP failures. The proposed water ripple algorithm maximizes the minimum delay difference, which is defined as the difference between transmission delay and tolerable delay, to satisfy requirements of multiple users simultaneously. Variable transmission power ranges (which involve cell breathing method types) and association management are adjusted to minimize the number of out-of-service mobile devices (MDs). Thus, fair allocation of resources to users and adequate QoS are satisfied.