Improved signal-to-noise ratio in EPI sequences with highly asymmetric spin echo and highly asymmetric STEAM preparations (HASE-EPI and HASTEAM-EPI)

Magnetic Resonance Materials in Physics, Biology and Medicine - Alternative versions of echo-planar imaging (EPI) sequences with standard spin echo (SE) or stimulated echo acquisition mode (STEAM)...     

Dithieno[3,2‐b:2′,3′‐d]pyrrol‐Cored Hole Transport Material Enabling Over 21% Efficiency Dopant‐Free Perovskite Solar Cells

Dopant‐free hole transport materials (HTMs) are essential for commercialization of perovskite solar cells (PSCs). However, power conversion efficiencies (PCEs) of the state‐of‐the‐art PSCs with small molecule dopant‐free HTMs are below 20%. Herein, a simple dithieno[3,2‐b:2′,3′‐d]pyrrol‐cored small molecule, DTP‐C6Th, is reported as a promising dopant‐free HTM. Compared with commonly used spiro‐OMeTAD, DTP‐C6Th exhibits a similar energy level, a better hole mobility of 4.18 × 10^?4 cm² V^?1 s^?1, and more efficient hole extraction, enabling efficient and stable PSCs with a dopant‐free HTM. With the addition of an ultrathin poly(methyl methacrylate) passivation layer and properly tuning the composition of the perovskite absorber layer, a champion PCE of 21.04% is achieved, which is the highest value for small molecule dopant‐free HTM based PSCs to date. Additionally, PSCs using the DTP‐C6Th HTM exhibit significantly improved long‐term stability compared with the conventional cells with the metal additive doped spiro‐OMeTAD HTM. Therefore, this work provides a new candidate and effective device engineering strategy for achieving high PCEs with dopant‐free HTMs.     

A new algorithm of modified binary particle swarm optimization based on the Gustafson-Kessel for credit risk assessment

Neural Computing and Applications - To increase the quality of loans provision and reduce the risk involved in this process, several credit scoring models have been developed and utilized to...     

Selective CO2 Capture and High Proton Conductivity of a Functional Star‐of‐David Catenane Metal–Organic Framework

Network structures based on Star‐of‐David catenanes with multiple superior functionalities have been so far elusive, although numerous topologically interesting networks are synthesized. Here, a metal–organic framework featuring fused Star‐of‐David catenanes is reported. Two triangular metallacycles with opposite handedness are triply intertwined forming a Star‐of‐David catenane. Each catenane fuses with its six neighbors to generate a porous twofold intercatenated gyroid framework. The compound possesses exceptional stability and exhibits multiple functionalities including highly selective CO₂ capture, high proton conductivity, and coexistence of slow magnetic relaxation and long‐range ordering.     

An Enhanced Cooperative Communication Scheme for Physical Uplink Shared Channel in NB-IoT

Wireless Personal Communications - Smart Home is one of the most established applications of the Internet of Things. Almost every equipment we use in our daily life—appliances, electric...     

Joint spectrum sensing and resource allocation optimization using genetic algorithm for frequency hopping–based cognitive radio networks

In cognitive radio (CR) networks, secondary users should effectively use unused licensed spectrums, unless they cause any harmful interference to the primary users. Therefore, spectrum sensing and channel resource allocation are the 2 main functionalities of CR networks, which play important roles in the performance of a CR system. To maximize the CR system utility, we propose a joint out‐of‐band spectrum sensing and operating channel allocation scheme based on genetic algorithm for frequency hopping–based CR networks. In this paper, to effectively sense the primary signal on hopping channels at each hopping slot time, a set of member nodes sense the next hopping channel, which is called out‐of‐band sensing. To achieve collision‐free cooperative sensing reporting, the next channel detection notification mechanism is presented. Using genetic algorithm, the optimum sensing and data transmission schedules are derived. It selects a sensing node set that participate the spectrum sensing for the next expected hopping channel during the current channel hopping time and another set of nodes that take opportunity for transmitting data on the current hopping channel. The optimum channel allocation is performed in accordance with each node's individual traffic demand. Simulation results show that the proposed scheme can achieve reliable spectrum sensing and efficient channel allocation.     

Highly Efficient Rapid Annealing of Thin Polar Polymer Film Ferroelectric Devices at Sub‐Glass Transition Temperature

An unexpected rapid anneal of electrically active defects in an ultrathin (15.5 nm) polar polyimide film at and below glass transition temperature (T_g) is reported. The polar polymer is the gate dielectric of a thin‐film‐transistor. Gate leakage current density (J_g) through the polymer initially increases with temperature, as expected, but decreases rapidly at T_g ? 60 °C. After ≈2 min at T_g, the leakage is reduced by nearly three orders of magnitude. A concomitant observation is that the drain current (I_d)–gate voltage (V_g) hysteresis decreases with temperature, reaching zero at nearly the same temperature at which J_g collapses. As J_g drops further, the drain current hysteresis increases again but in the opposite direction. This combination strongly supports the interpretation of rapid defect annealing.     

Influences of the valley morphology and rock mass strength on tunnel convergence: With a case study of Khimti 1 headrace tunnel in Nepal

Underground structures are constructed at the bottom of the valley sides for various purposes and for different reasons. Hydropower projects and transport tunnels are some of the examples of such structures. In this paper, literatures on topographical effects on the in situ stresses in valley and fjord sides are reviewed. An attempt is made to correlate stress anisotropy problems with the valley side topography by using Phase² numerical modelling. Based on an underground construction case study, fifteen in situ stress measurements and the Phase² analysis, stress induced problems have been found to be influenced by the valley morphology. This influence can be monitored by the convergence measurement and by the stress measurement. In addition to the overburden height, the total valley height and the slope need to be considered in the assessment of the stress induced problem. The second aspect dealt with is the influence of the rock strength on the tunnel convergence. In the Khimti 1 headrace tunnel and 66 cases from 15 countries, it has been observed that the tunnel convergence is larger in the weaker rocks than in the stronger rocks though they may have similar Q-values. Rock type such as gneiss or phyllite (corresponding to the rock mass strength) is not considered in the Q-system but it has influence on the convergence that takes place in underground works. Thus, it also needs to be considered in the assessment of potential convergence of an underground structure.