bluuebunny/crossref_metadata_2025 huggingface dataset:
Magneto-Aeroelastic Dynamic Buckling and Flutter of Rotating Conductive Annular Disks Under Air-Film Loading
Authors: Li Wenqiang , Liang Shuqi , Hu Yuda , Wang Chien Ming
Published: September 2024

This paper focuses on the magneto-aeroelastic dynamic buckling and flutter generated by traveling waves of rotating conductive disks under air-film loading. A distributed time-variable aerodynamic model is derived by using the Navier–Stokes (NS) equation and the lubrication theory. The electromagnetic force on the disk is modeled by using the electromagnetic theory. Based on Kirchhoff’s theory and considering the rotating centrifugal effect, the dynamic equations for magnetic-aeroelastic coupling are established by using the Hamiltonian principle. Bessel functions are assumed for the mode shapes, and the steady-state properties of the aerodynamic equations are presented that allow for the derivation and decoupling of the coupling differential equations in the Galerkin approach of Hilbert space. The effects of the magnetic field intensity, rotational speed, and aerodynamic parameters on the magneto-aeroelastic buckling instability and flutter characteristics generated by backward traveling wave instability are investigated, respectively. The numerical calculations show the damping effect of the magnetic field, which increases magnetic field intensity and suppresses buckling instability and flutter. Moreover, the sensitivity of the system with respect to magnetic field intensity demonstrated that, for high-order mode instability, a critical instability region (CIR) emerges with changes in the magnetic field intensity, whereby a distribution with a very small frequency may induce dynamical buckling instability of the system. Additionally, the rotational speed escalates to reach either the critical speed or flutter speed, the system may experience dynamic buckling or flutter instability characterized by divergent response or equal-amplitude vibration, respectively.
A NOVEL SLEEP STAGE CLASSIFICATION METHOD FOR ELDERLY PEOPLE USING THE SLEEP EEG SIGNAL AND SENET MODELS
Authors: SHI MIN , XU LIJUN , QU HANGYU
Published: September 2024

First, research on sleep stage staging in older individuals is highly valuable because it helps to obtain insights into sleep quality and structure changes that occur in older persons. This approach was used to better understand the correlations with cognitive functioning, the immune system, and mental health, among other factors. Second, identifying the features of older persons in various stages of sleep could lead to more specific guidance for managing and treating personalized sleep to significantly improve the quality of life of these individuals. Finally, in-depth research on sleep in older persons can assist in the development of preventative and intervention measures for older adults, which can help to reduce the negative consequences that age-related sleep issues have on general health. Categorizing sleep EEG data is the focus of this research to present an improved squeeze-and-excitation network (SENet) for application in the classification process. For the purpose of this study, electroencephalogram (EEG) features were extracted using continuous wavelet transform. Subsequently, the lightweight context transform (LCT), which is a combination of normalization, linear transformation, and SENet, is carried out to achieve sleep EEG classification. Extraction using the continuous wavelet transform has the potential to more accurately depict the changes and characteristics of sleep stages. As a result of incorporating LCT, the computational cost of the model is reduced, and the model becomes more applicable to real-world situations. Experiments conducted on two public datasets, Sleep-EDF-20 and Sleep-EDF-78, demonstrated that the strategy presented in this study can achieve the requisite classification performance and the model converges faster.
REVIEW ON EVALUATION METHODS OF FRACTURE HEALING
Authors: WANG MONAN , ZHENG SIYUAN , GAO SU , LI PENGCHENG , CUI SONG , XIA LINGBING
Published: September 2024

Fracture is one of the most important health problems in people’s life. Millions of people have fractures every year. However, there is no unified standard for fracture healing in the clinic. Most definitions of complete fracture healing are subjective evaluations based on X-ray films. However, it is not reliable to evaluate the biomechanical strength of bone according to the number of callus on X-ray, and the imaging time of callus lags behind the actual callus, which is not conducive to the evaluation of early fracture healing time. In addition, although more and more fracture patients have achieved imaging healing after injury, the bone quality and bone strength of the whole body and local fracture have not returned to the normal level, and the probability of re-fracture has increased significantly, which has brought great pain to their families. Fracture healing is affected by many factors, such as age, fracture site, whether to fix the fracture site, and osteoporosis. Therefore, when evaluating the fracture healing status of patients, we should not only evaluate whether the fracture is healed but also evaluate its healing. By analyzing the previous research methods of fracture healing, in this paper, we systematically summarize the evaluation methods of fracture healing from the perspectives of computer tomography, ultrasound, bone density, biosensors, and biomechanics by analyzing previous research methods of fracture healing, aiming to provide reference for researchers in related fields.
EXPLORING VITAMIN D-RELATED KAP INFLUENCING FACTORS IN MIDDLE-AGED AND ELDERLY PATIENTS WITH ANKLE FRACTURES: A LOGISTIC REGRESSION AND DECISION TREE MODEL-BASED STUDY
Authors: LIANG YU , ZHANG GUANGLEI
Published: September 2024

This study aimed to analyze the factors influencing vitamin D (VD)-related knowledge, attitude, and practice (KAP) in middle-aged and elderly patients with ankle fractures using the binary logistic regression and decision tree models, thereby providing scientific evidence for VD-related recovery strategies. A Chinese version of the nutrition KAP questionnaire was administered in a Grade III A Hospital using random sampling for the investigation. Meanwhile, the factors influencing KAP were analyzed using the aforementioned two models. The results of the binary logistic regression model showed that the patient age [odds ratio [Formula: see text]; 95% confidence interval (CI): 0.117–0.295], spouse education ([Formula: see text]; 95% CI: 0.267–0.422), and spouse occupation ([Formula: see text]; 95% CI: 1.078–1.693) were the factors influencing VD-related KAP. The decision tree chi-squared automatic interaction detector (CHAID) algorithm showed that spouse education, patient age, and living room lighting were the influencing factors, among which spouse education was the most important. VD in middle-aged and elderly patients with ankle fractures was affected by the age and the education level of the spouse. These two models can analyze the influencing factors of knowledge and practice, and can be used together to complement each other.
A STUDENT SENTIMENT ANALYSIS METHOD BASED ON MULTIMODAL DEEP LEARNING
Authors: KONG LIDAN , YAO JIAN , SHEN JINSONG , GU YI
Published: September 2024

Based on electroencephalography (EEG) and video data, we propose a multimodal affective analysis approach in this study to examine the affective states of university students. This method is based on the findings of this investigation. The EEG signals and video data were obtained from 50 college students experiencing various emotional states, and then they were processed in great detail. The EEG signals are pre-processed to extract their multi-view characteristics. Additionally, the video data were processed by frame extraction, face detection, and convolutional neural network (CNN) operations to extract features. We take a feature splicing strategy to merge EEG and video data to produce a time series input to realize the fusion of multimodal features. This allows us to realize the fusion of multimodal features. In addition, we developed and trained a model for the classification of emotional states based on a long short-term memory network (LSTM). With the help of cross-validation, the experiments were carried out by dividing the dataset into a training set and a test set. The model’s performance was evaluated with the help of four metrics: accuracy, precision, recall, and F1-score. When compared to the single-modal method of sentiment analysis, the results demonstrate that the multimodal approach, which combines EEG and video, demonstrates considerable advantages in terms of sentiment detection. Specifically, the accuracy obtained from the multimodal approach is significantly higher. As part of its investigation, the study also investigates the respective contributions of EEG and video aspects to emotion detection. It discovers that these features complement each other in a variety of emotional states and have the potential to improve the overall recognition results. The multimodal sentiment analysis method that is based on LSTM offers a high level of accuracy and robustness when it comes to recognizing the affective states of college students. This is especially essential for enhancing the quality of education and providing support for mental health.
HAND TREMOR DETECTION AND FEEDBACK SYSTEM BASED ON INERTIAL MEASUREMENT UNIT FOR PARKINSON’S DISEASE: A PILOT STUDY
Authors: KWON IL-JUNG , KIM HYEONJONG , KO JUNGHYUK
Published: September 2024

The hand tremor symptoms of Parkinson’s disease (PD) patients are expressed in a wide variety of forms. These tremors are not limited to specific areas, but the most experienced by PD patients are hand-related. To detect such hand tremor symptoms, a device based on an inertial measurement unit (IMU) was used to measure changes in the vibration speed around the wrist. The sensor data collected from the gyroscope through a dedicated algorithm can be reflected to convert it into a result value of the number of tremors of the user, and hand tremor characteristics can be extracted. The performance of the system was validated using a hand tremor simulator. The experiments confirmed that the algorithm operated normally under the specific conditions set (5–18[Formula: see text]Hz) for hand tremor detection, and the operation results matched those of the theoretically detectable range. The wearable device can measure the user’s bio-kinetic signals in daily life using a gyroscope, adjust the algorithm’s sensitivity based on the severity of tremor symptoms, and continuously monitor symptoms by transmitting the recognition results via Bluetooth communication.
JOINT LOW-RANK REPRESENTATION AND TRANSFER MULTI-VIEW LEARNING APPROACH FOR EEG EPILEPSY CLASSIFICATION
Authors: ZANG HAO , JIAO LEI , QIN TAO , QIAN JIANSHENG
Published: September 2024

Classification of epileptic electroencephalograms can provide strong technical support for early warning and monitoring of epilepsy. However, Electroencephalogram (EEG) has characteristics of specificity, multi-feature, and susceptibility to noise interference. Therefore, this paper proposes a joint low-rank representation and transfer multi-view learning (LRR-TML) approach for EEG epilepsy classification. The LRR-TML approach inherits the advantages of low-rank representation, filters redundant features and noise information, and focuses on the main feature and significant feature of EEG. The LRR-TML approach introduces the ideas of transfer learning and multi-view learning on the framework of low-rank representation, mines the linear correlation between different domains in the subspace through low-rank representation, and effectively transfers the discriminative knowledge of the source domain to the target domain. According to the principles of complementarity and consistency of views, the LRR-TML approach comprehensively describes EEG by integrating various features, maximizing the consistency between different views and minimizing the divergence between views. Experimental results on the Bonn dataset show that the LRR-TML approach achieves the best classification results among all comparison approaches.
MEDICAL IMAGE RESTORATION METHOD BASED ON NEIGHBORHOOD REGISTRATION AND ITS APPLICATION
Authors: YOU YAXIONG , SHI XUNJIE , LIU ZHE , WANG RUI , LI CHONGJI , YANG YANLONG
Published: September 2024

In this paper, due to factors such as imaging devices and imaging environment, medical images may experience halos, blurring, and unclear contrast. A medical image restoration method based on neighborhood registration is proposed to address this issue. In this repair method, the image is first processed into blocks, then the blocks that need to be repaired are determined. Afterward, based on the surrounding neighborhood information of the image block to be repaired, the image information within the optimal neighborhood block is repaired and replaced. The experimental results show that the repair method based on the best neighborhood registration has completed medical image restoration, with significantly higher repair quality than the reference method. The repaired image results have a high RSNR.
A SIMPLE NONPOWERED HAND REHABILITATION DEVICE CAPABLE OF ADJUSTING THE INDIVIDUAL FINGER LOAD: A PILOT STUDY
Authors: CHOI JIN-SEUNG
Published: September 2024

Hemiplegia, which is a frequent sequela of stroke, significantly impairs patients’ ability to perform activities of daily living. While the recovery rate of lower limb motor function through rehabilitation exercise is high, the recovery rate of hand function is relatively low. This study developed a nonpowered hand rehabilitation device for hand rehabilitation exercises of hemiplegic patients who can exercise on their own. The structure of the frame was minimized and 3D printed for personal customization. A prototype of a nonpowered hand rehabilitation device with a lightweight and simple structure was produced by using a spring instead of a motor as a power source. In addition, the effect of the elastic modulus (EM) of the spring connected to the finger on the grasping motion was examined for each finger. By assessing the EM-dependent changes in the force exerted by each individual finger and the adjacent digits, this study established the feasibility of using this device for rehabilitation exercises tailored to specific fingers or movements. Although additional research is needed on hemiplegic patients, this device is expected to increase the efficiency of hand rehabilitation exercises for early stroke patients due to its lightweight and simple structure.
IMPACT OF REHABILITATION TRAINING COMBINED WITH VISUAL FEEDBACK BALANCE TRAINING ON MOTOR FUNCTION IN PATIENTS WITH SPORTS-RELATED KNEE INJURIES: A BIOMECHANICAL APPROACH
Authors: JI QINGFEN , LI XIAOFEN , ZOU GUANGYI , PAN HONGYING
Published: September 2024

Objective: This study aimed to evaluate the effect of rehabilitation training combined with visual feedback balance training on motor functions in patients with knee injuries. Methods: A total of 80 patients with sports-related knee injuries from the outpatient and inpatient departments of Lishui City People’s Hospital were randomly divided into control and observation groups, with 40 patients in each group. The control group underwent rehabilitation training based on biomechanical principles, and the observation group underwent additional visual feedback balance training. Trunk control ability, limb motor function, and walking stability were compared between the two groups before, 1 month after, and 3 months after training. Results: After 1 month of training, the lower-limb function scores, trunk control ability scores in activities such as turning to the healthy side and the affected side on the bed, sitting and standing balance, and scores for Dynamic Gait Index and Berg balance scale were all higher in the observation group compared with the control group ([Formula: see text]). After 3 months of training, the differences in scores between the two groups became more pronounced ([Formula: see text]). Conclusions: Rehabilitation training based on biomechanical principles combined with visual feedback balance training effectively improved the limb motor function, enhanced the trunk control ability, and maintained the body balance and walking stability in patients with sports-related knee injuries. This study provided a more effective novel rehabilitation approach for the postoperative recovery of patients with knee injuries.
Influence of Zinc Ion Concentration on the Structural, Surface Morphology and Optical Properties of Zinc Selenide Thin Films
Authors: Hile D. D. , Koao L. F. , Swart H. C. , Motloung S. V. , Ahemen I. , Ndlangamandla C. L.
Published: September 2024

ZnSe thin films were deposited on nonconducting glass substrates using different Zn[Formula: see text] ion concentrations. The films were deposited at 80[Formula: see text]C for 2.0[Formula: see text]h via photo-assisted chemical bath technique and annealed for 2.0[Formula: see text]h at 250[Formula: see text]C. X-ray diffraction revealed a hexagonal structure with preferred orientation along the (002) plane and the average crystallite size decreased from 10.5[Formula: see text]nm to 6.8[Formula: see text]nm with increased Zn[Formula: see text] ions. Raman spectra were used to confirm ZnSe phonon modes whose intensity increased with Zn[Formula: see text] ion concentrations although with fluctuation. Optical analysis showed higher absorbance and low transmittance in the visible region than near infrared making the thin films good materials for selective absorber surfaces. The band gap increased from 2.52[Formula: see text]eV to 2.78[Formula: see text]eV as the Zn[Formula: see text] ion concentration varied from 0.05% to 0.25%. The presence of the desired elements was confirmed by the EDS. Photoluminescence studies revealed three emission peaks which were all ascribed to defect state levels in ZnSe and all the samples emitted in reddish color according to CIE color chromaticity analysis. The selective absorption, wide band gap and broad emission properties suggest that the material is promising for optoelectronic applications.
Combinatorial algorithms for the minmax robust median subtree problem on tree networks with interval vertex weights
Authors: Nguyen Kien Trung , Nguyen-Thu Huong , Le Huy Minh , Hiep Tran Thanh
Published: September 2024

The typical median subtree problem on trees is to locate a (continuous) tree-shaped facility (the leaves of this facility are not necessary vertices) with a specified length to minimize the total weighted distance of all vertices to the new facility. In this paper, each vertex weight can be any value within an interval and the total deviation of weights is limited within a threshold. We want to find a subtree that minimizes the median function in the worst-case scenario. This is the so-called minmax robust median subtree problem on trees. In order to solve the problem, we first consider the minmax robust 1-median problem on trees and solve the problem in [Formula: see text] time. Then, the nestedness property is coined, i.e., any optimal subtree must contain a robust 1-median in the tree. Based on this property, we develop a greedy algorithm that solves the corresponding problem in [Formula: see text] time.
Techno-finance Literacy and Company Performance: Mediating Role of Risk Management Practices based on Structural Equation Modeling
Authors: Suryani Embun , Diswandi Diswandi , Afwani Royana
Published: September 2024

This study aimed to develop a structural model to explore the dynamic model of small and medium-sized enterprise (SME) performance, technological and financial literacy (techno-finance literacy), and risk management (RM) practices. Data collected from 285 SMEs in Lombok, Indonesia was analyzed using PLS-SEM regarding techno-finance literacy. The data analysis is presented using both quantitative and qualitative descriptive approaches. The results indicated that technological and financial literacy contribute significantly to SME performance. Additionally, RM practices affect SME performance, and partially mediate the effect of technology and financial literacy on SME performance. Therefore, the managerial implications of this study show that SMEs must adopt technology in running their businesses if they wish to improve performance and manage financial risks. The adoption of technology will help SMEs overcome their weaknesses and reduce risk.
MSME AWARENESS OF ISLAMIC PROFIT AND LOSS SHARING IN BRUNEI DARUSSALAM
Authors: NJAWAYA RUVIMBO , SALLEH PG MD HASNOL ALWEE PG HJ MD
Published: September 2024

In Islamic finance, Profit and Loss Sharing (PLS) concepts are widely advocated as one of the most equitable concepts available for Islamic Financial Institutions (IFIs), given the equitable nature of sharing one’s profit and loss. However, in practice its use is limited as challenges exist which include moral hazard and a mismatch of the competencies of contemporary IFIs vis-a-vis the risk profile of PLS concepts. These challenges of PLS from an IFI perspective had been extensively covered in the literature, therefore this paper attempts to assess the challenges of PLS from a consumer or demand perspective. It is argued that there should be a reasonable level of awareness and willingness for consumers to demand a particular product; it is economically inefficient to create a product for which demand is lacking. Using a mixed method research design which includes surveys to 177 MSMEs and semi-structured interviews with two Islamic finance academicians, the findings indicate a low-level awareness of Mudarabah and Musharakah amongst MSMEs. Further, the willingness to use PLS financing among MSMEs is also found to be low, notably in terms of the willingness to share profits with IFIs, as well as having reservations on IFIs to be involved in playing an operational role in the small enterprise. These findings prompt the need for enhanced marketing approaches to enhance the awareness of these concepts for MSMES, and at the same time, defining a selective target market to explore the willingness amongst MSMEs, should PLS financing be widely available in Brunei.
Birds of a Feather Born Together? On Siblings, Crime, and Criminal Legal System Contact
Authors: Wakefield Sara , Baker Garrett
Published: September 2024

Classic criminological scholarship emphasizes sibling correlations in delinquency, criminal offending, and system contact. This foundational work, however, has mostly not translated to a rich contemporary research agenda on whether and how siblings influence one another—an unfortunate omission given that siblings spend significant time together throughout the life course. Our review, therefore, has one overarching goal: to invigorate the criminological study of siblings in an era of increasingly complex and varied family systems. We trace the sporadic criminological literature on siblings over the past half-century and document the relative absence of research on siblings in core criminology journals. In so doing, we lean on interdisciplinary scholarship to argue that siblings have been both undertheorized and underanalyzed in criminology, highlight the practical barriers and causal identification challenges to isolating so-called sibling spillovers, and rummage the limited landscape of recent empirical research for insights to push the field forward.
Britain's Liability-Driven Investment Episode Was a Canary No One Elsewhere Bothered to Think About
Authors: Tucker Paul M.W.
Published: September 2024

Britain's liability-driven investment crisis in fall 2022 had lessons for other major financial centers that, as evidenced by the US and Swiss banking crises only a few months later, were largely ignored. They are still relevant. In this article, I first discuss what drove the British crisis before identifying lessons for the microregulation of pension funds; for financial stability policy on shadow banking and beyond; for central banking balance sheet regimes, including lending of last resort and market making of last resort; and for monetary policy when fiscal policy makers sit on their hands.
Direct Determination of Metallic Contamination on and in Wafers Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry
Authors: Kawabata Katsu , Ichinose Tatsu , Suzuki Koshi
Published: September 2024

A new analytical technique was developed for determination of metallic impurities in wafers using LA-GED-MSAG-ICP-MS. Up to 300 mm wafer can be analyzed directly without using a small, enclosed chamber. Particles generated by a femto-second laser ablation were aspirated together with a particle free clean air by an ejector and introduced to the ICP-MS (Inductively Coupled Plasma Mass Spectrometry) via GED (Gas Exchange Device). The air was exchanged by Ar gas and the particles came out from GED in Ar gas stream. For quantitation of LA-ICP-MS, MSAG (Metal Standard Aerosol Generation) was used. MSAG could introduce nearly a 100% of aqueous multi-element standard solution to the plasma of ICP-MS, which allowed precise quantitation using the method of standard addition while ablating wafer samples. This paper describes how the new analytical technique works for ultra-trace level of metallic impurities in wafers.
(Invited) Mobility Enhancement Technology of Extremely-Thin Body Ge-on-Insulator Channel Mosfets
Authors: Takagi Shinichi , Han Xueyang , Chen Chia-Tsong , Sumita Kei , Toprasertpong Kasidit , Takenaka Mitsuru
Published: September 2024

An extremely thin body (ETB) channel is mandatory for scaled nano-sheet structures to realize continuous miniaturization of CMOS devices. Here, mobility booster technologies to maintain high channel mobility are strongly needed, because surface roughness scattering significantly reduces mobility in such ETB channels. From this viewpoint, Ge-On-Insulator (GOI) or SiGe-On-Insulator (SGOI) channels are promising because of the low electron and hole effective mass along channel directions. It is theoretically shown that (111) GOI n-MOSFETs can hold high electron mobility even in the body thickness down to 2 nm. Thus, (111) GOI structures and n-MOSFETs are fabricated, and the electrical characteristics are studied. For p-MOSFETs, on the other hand, (110) surface orientation and application of compressive strain are still effective in boosting hole mobility in ETB channels. Here, (110) asymmetric compressive strain SGOI p-MOSFETs are experimentally demonstrated, and the body thickness dependencies of the effective mobility are examined.
The Lattice Strain Distribution in GexSn1-x Micro-Disks Investigated at the Sub 100-nm Scale
Authors: Corley-Wiciak Cedric , Zöllner Marvin Hartwig , Corley-Wiciak Agnieszka Anna , Rovaris Fabrizio , Sfruncia Gianfranco , Nicotra Giuseppe , Zaitsev Ignati , Manganelli Costanza Lucia , Zatterin Edoardo , Spirito Davide , Marzegalli Anna , Schulli Tobias , Von Den Driesch Nils , Buca Dan , Montalenti Francesco , Richter Carsten , Capellini Giovanni
Published: September 2024

Experimental assessment of the strain tensor within a microstructure is challenging, especially for small mechanical deformations acting over submicron length scales. In this work, we fully characterize the spatial strain distribution within a suspended micro-disk laser made of Ge1-xSnx alloy, with fine resolution <200 nm. We employ Scanning X-ray Diffraction Microscopy, a model-free method based on synchrotron radiation, to directly obtain maps of all components of lattice strain and rotation, including the shear strains, finding them on a magnitude ~10-3. We correlate these small elastic deformations to structural defects and the relaxation of the three-dimensional microstructure, demonstrating the potential of an advanced X-ray microscopy technique for microelectronics.
Advanced SiGe:B Raised Sources and Drains for p-type FD-SOI MOSFETs
Authors: Hartmann Jean-Michel , Aussenac Francois , Glorieux Olivier , Cooper David , Kerdilès Sebastien , Chalupa Zdenek , Boulard Francois , Niebojewski Heimanu , Duriez Blandine , Bordignon Thomas , Peru Sebastien , Michałowski Pawel , Daubriac Richard , Cristiano Fuccio
Published: September 2024

We have evaluated the feasability of selectively growing, with a chlorinated chemistry, 20 to 30 nm thick SiGe:B Raised Sources and Drains with Ge concentration gradients (from 50% down to 20%-30%, typically) on each side of FD-SOI transistors. The motivation was twofold: (i) inject meaningful amounts of compressive strain in the channel of p-type MOS devices thanks to high Ge concentrations in layers sitting in the same plane than Si or SiGe channels and (ii) benefit from lower Ge concentration SiGe layers on top that are easier to germano-silicide. Growing a thin Si(:B) cap on SiGe:B otherwise yields more uniform and stable contacts. We have thus studied the Si capping of SiGe 20% or 30% layers. As growth has to be conducted, for Si, at temperatures significantly higher than that of SiGe (750°C, to be compared with 700°C for SiGe 20% and 650°C for SiGe 30%, typically), we have quantified the impact of using temperature ramping-ups with SiH2Cl2 + HCl flowing into the growing chamber. The purpose of such active ramps was to prevent elastic strain relaxation, e.g. the formation of SiGe surface undulations that would happen with temperature ramps under H2 only.
Comprehensive study on epitaxial growth of GeSn(111) layers with high Sn content on Si(111) featuring Ge buffer layer
Authors: Shibayama Shigehisa , Mori Shunsuke , Kato Yoshiki , Sakashita Mitsuo , Kurosawa Masashi , Nakatsuka Osamu
Published: September 2024

The study comprehensively discussed the crystalline properties of GeSn(111) epitaxial layers on Si(111) using Ge double buffer layers toward the formation of the direct transition GeSn(111) with a Sn content around 10%. We found that the introduction of Ge double buffer layers is rather effective to improve the crystallinity of GeSn(111) than the single buffer case. However, thicker Ge buffer layer degrades the crystallinity of GeSn(111) because the strain relaxation of GeSn layer is likely to occur. In this study, through optimizing the thicknesses of Ge buffer layers formed at low and high temperatures (LT-Ge and HT-Ge, respectively), it was clarified that 100 and 500 nm for LT- and HT-Ge thicknesses, respectively, are suited to realize a high quality GeSn(111). The grown GeSn(111) epitaxial layer includes a Sn content of ~8–11% with a compressive strain of ~1–2%, which is contained within the region of direct transition GeSn(111).
Improved Electrical Performance of CVD Monolayer-MoS2 TFT Via Wet Transfer of Van Der Waals Source/Drain Electrodes
Authors: Deng Yuheng , Sun Hao , Wang Qing He , Xu Jingping , Lai Pui To
Published: September 2024

In this study, we introduce a novel wet transfer method utilizing PMMA as a supporting tool for electrode transfer, with HF employed to facilitate the separation of the electrode from a sacrificial layer. This method is applied to fabricate source/drain electrodes for MoS2 FETs. The implementation of the transferred Ag source/drain electrodes significantly enhances the carrier mobility of the CVD monolayer-MoS2 FET by forming a Van der Waals contact between the monolayer MoS2 and the Ag electrode, which ensures minimal contact resistance between them. As a result, compared with its counterpart with Ag source/drain electrodes prepared by thermal evaporation, the field-effect mobility of the proposed MoS2 FET is increased from 25.3 cm²V⁻¹s⁻¹ to 69.1 cm²V⁻¹s⁻¹, while the contact resistance is reduced from 13.7 kΩ·μm to 1.49 kΩ·μm.
Four-Terminal Polycrystalline-Silicon Vertical Thin-Film Transistors on Glass Substrates for pH Sensor Applications
Authors: Suzuki Kosei , Nitta Masahide , Tabei Tetsuo , Hara Akito
Published: September 2024

We developed polycrystalline silicon (poly-Si) vertical thin-film transistors with a four-terminal structure. The TFT has two gates, called the top gate (TG) and bottom gate (BG), at opposite sites of the vertical poly-Si channel. The TG and BG are connected to the sensor and detection circuit, respectively. The variations in the pH of the solution were successfully detected by varying the output voltage of the outer circuit.
(Invited) In-situ Observation of Silicon Carbide Solution Growth: Observation Principle and Effect of Al Addition to Si-Cr Solvent
Authors: Kawanishi Sakiko , Yamada Tomohiro , Daikoku Hironori , Shibata Hiroyuki , Yoshikawa Takeshi
Published: September 2024

The in-situ interface observation of silicon carbide (SiC) solution growth effectively elucidates various phenomena occurring at the growth front. To investigate this observation technique from the perspective of the optical transmission properties of SiC, the optical absorption properties of 3C-, 4H-, and 6H-SiC were measured over a wide range of temperatures. The obtained absorption properties indicate the optical conditions necessary for in-situ observation and the possibility of identifying different polytype inclusions. Furthermore, the effect of Al addition to the Si-Cr solvent on the SiC growth interface, where Al addition is known to be effective for growing high-quality SiC, was investigated by in situ observations. It was clarified that the presence of Al suppressed the formation of step pinning, resulting in preventing the formation of bunching steps and subsequent roughening of the growth interface.
Relationship between synthesis conditions and ORR activity of PtCo nanowire/C catalysts for PEFC cathodes
Authors: Shibata Kousuke , Takeguchi Tatsuya , Wakita Hidenobu , Ui Koichi , Garavdorj Batnyagt
Published: September 2024

Nanowire (NW) structures have attracted attention as durable catalysts for the oxygen reduction reaction (ORR) due to their resistance to aggregation, unique morphology, and efficient electron conduction. However, NWs often suffer from limited structural stability, and there is a lack of research on their performance in membrane electrode assembly (MEA) studies. In this study, PtCo NW/C catalysts with various amounts of oleylamine (OAm) were prepared, and their oxygen reduction reaction (ORR) activity and durability were investigated by MEA and RDE testing conditions. XRD analysis and TEM observations showed that the prepared PtCo NWs were successfully alloyed,and PtCo NW alloys were observed. CV and LSV results showed that the PtCo NW/C OAm100 catalyst with 2 h of acid treatment had the best ORR activity. The I-V test results demonstrated that the PtCo NW/C OAm100 catalyst with 2 h of acid treatment had higher cell voltage, and cell performance was also excellent. It was found that the ORR activity of PtCo NW was improved by adding the appropriate amount of OAm.
Advanced Free Radical Scavenger for Proton Exchange Membrane Fuel Cells
Authors: Wang Liang , Jia Hongfei
Published: September 2024

Yttrium doped cerium oxide (CeO2·Y2O3) was studied as a free radical scavenger for proton exchange membrane fuel cells (PEMFCs). The CeO2·Y2O3 was compared with pure CeO2 in MEAs with and without the free radical scavenger. Membrane Electrode assembly (MEA) after open circuit voltage (OCV) hold accelerated stress test (AST) show better performance retention with CeO2·Y2O3 than CeO2. CeO2·Y2O3 and CeO2 show slightly improved performance than pristine MEA without free radical scavenger. X-ray fluorescence (XRF) confirmed the improved Ce ions retention with CeO2·Y2O3 than pure CeO2, indicating improved stability of CeO2 after doping with Yttrium. Furthermore, ex-situ Fenton study with inductively coupled plasma mass spectrometry (ICP-MS) analysis shows better stability of Ce in CeO2·Y2O3. This study shows that yttrium-doped cerium oxide has better stability against dissolution and enhances the stability of polymer components against free radicals than CeO2.
Development of a Superior Anion Exchange Membrane with Hyperbranched Polymer for Anion Exchange Membrane Water Electrolysis
Authors: Palanivel Tamilazhagan , Kalanur Shankara , Rajangam Vinodh , Pollet Bruno Georges
Published: September 2024

The production of hydrogen using membrane-based electrolyzersposes significant advantages and benefits compared to traditionalelectrolysis methods. Among the electrolyzers, anion exchangemembrane water electrolysis (AEMWE) has emerged as one of thepromising technologies owing to its unique advantages. However,the development of efficient AEMs for water electrolysis presentssignificant challenges, particularly in achieving enhanceddimensional stability and conductivity. In this study, ahyperbranched polyesteramide (HPEA) was synthesized andblended with poly(ether sulfone) (PES) to address the challenges.The resulting QPES-HPEA blend membrane exhibited a lowswelling ratio and high water uptake, which are critical formaintaining dimensional stability and enhancing the hydroxide iontransport efficiency of AEM. The enhanced physical properties andoptimized structure of the membrane make it a promising candidatefor next-generation AEMs in water electrolysis systems.
Stepwise Crystallization and Mass Transport Limitations in Annealed SPEEK Thin Films
Authors: GAO Xiao , Guo Keyu , Cui Hong , Huang Chun , Niu Yao , Chen Yu , Ohta Noboru , Yi Wenbin
Published: September 2024

Pt-supported SPEEK (sulfonated poly ether ether ketone) thin films, mimicking the ionomer-electrode interface in polymer electrolyte fuel cells (PEFCs), were synthesized with thicknesses from 12 to 105 nm. Their glass transition temperature (Tg) was analyzed via in-situ thermal ellipsometry, revealing a thickness-dependent Tg decrease, indicative of confinement effects. Particularly, a 30 nm film, typical of practical ionomer films, exhibited surface crystallization preceding that at the buried interface, a phenomenon linked to higher mobility at the free surface, as con-firmed by grazing incidence wide-angle X-ray scattering (GI-WAXS) at both sub-critical (0.09º) and supercritical (0.14º) angles. This study elucidates the dynamic interplay between the high-mobility free surface and the interaction-intensive buried interface in confined SPEEK thin films. It was observed that below 30 nm thickness, interfacial interactions become the primary factor influencing transition temperature. Additionally, spatially heterogeneous crystallization, more pronounced in the out-of-plane direction, correlates with reduced proton conduction.
Bimodal Behavior of Catalyst Layers Prepared By Electrospray: High Water Uptake and Superhydrophobicity
Authors: Garcia-Salaberri Pablo A. , Merino Susana , de Diego Gonzalo , Duque Luis , Shahzad Hasan , Diaz-Alvarez Ester , Folgado M. Antonia , Chaparro Antonio M
Published: September 2024

Electrosprayed catalyst layers (CLs) for electrodes of proton exchange membrane fuel cells (PEMFCs) combine high water vapor uptake with a superhydrophobic character. Such ‘bimodal behavior’ is the basis for their high performance as cathode in PEMFC, and must be explained in the light of the film morphology resulting from the electrospray deposition process. A microscopic analysis of the deposited films, covering different scales, reveals important differences in particles and ionomer distribution between the electrosprayed and sprayed layers. The resulting electrosprayed CL shows pore surfaces covered by dendritic structure that provide the superhydrophobic character. Other experimental evidences point to an specific interaction of the ionomer with the catalyst in electrosprayed films.
Niobium Interlayer Coating: Is it a Practical Approach to Tune the Protective Pt Loading in PEM Water Electrolyzers?
Authors: Kalhori Hossein , Johar Mohammadhossein , Moradizadeh Leila , Shahgaldi Samaneh
Published: September 2024

Proton exchange membrane (PEM) water electrolysis is a pioneering and promising method for sustainable green hydrogen generation. However, the high cost of PEM water electrolyzer components poses a significant barrier to the commercialization and widespread application of this technology. In this research, a novel Niobium-Platinum coating is developed for the porous transport layer (PTL) to reduce the precious metal loading. Niobium (Nb)-based coating was applied as an interlayer between Pt and titanium (Ti) felt substrates to increase the adhesion of Pt. For this study, pulsed laser deposition (PLD) technique was applied for the first time to coat Nb and Pt multilayers onto Ti felt substrates. The results demonstrate that incorporating a Nb coating as an interlayer lead to reducing the Pt loading, which holds promise for the practical application of PTLs in PEM water electrolyzers.
(Invited) Development of Novel Coatings on Stainless Steel based Bipolar Plates for Proton Exchange Membrane (PEM) Water Electrolyzer Application
Authors: Singh Aditya , Shahgaldi Samaneh
Published: September 2024

The stainless steel (SS) is an appropriate material for bipolar plate of PEM water electrolyzer owing to its high electron transport, superior mechanical characteristics, and formability, but it needs a coating to increase corrosion resistance. Herein, the multilayer coating of Au/Cr/Au on the SS was developed by electroplating method and corrosion studied were performed for bipolar plate application of PEM water electrolyzer. The gold striking underlayer on the SS substrate passivated the surface oxides and facilitated a dense electroplated chromium layer. Furthermore, a uniform gold protective layer was electroplated on the chromium coated substrate to achieve a promising anti-corrosive property. The Au/Cr/Au 316L SS substrate presented approximately ten times lower corrosion current density, and positive shift of corrosion potential as compared to uncoated SS substrate. The Au/Cr/Au/ 316 L SS was analysed for long time, and it depicted slower corrosion as compared to without striking underlayer of gold (Au/Cr/ 316L SS).
Enabling Low Iridium Loadings and Reduced Catalyst Material Cost for PEM Water Electrolyzers Via Composite Anode Design with Conductive Additive
Authors: Ferner Kara J , Litster Shawn
Published: September 2024

Herein, we present the successful implementation of a composite anode using a conductive additive to enable low iridium (Ir) loadings for PEMWE while maintaining high-performance operation. We use platinum (Pt) black as the conductive additive given its high electrical conductivity, high stability, and a price currently one-fifth that of Ir. Using a high loading of Pt black conductive additive allowed for retained electrode thickness, good dispersion of Ir particles, and drastically decreased sheet resistance at low Ir loadings of 0.10 mgIr cm-2. Compared to a standard Ir oxide anode with high, commercially relevant Ir loading, a composite anode with a low loading of 0.10 mgIr cm-2 achieved an equal current density performance at 1.8 V, translating to a 95% reduction in loading and 80% cost reduction of the anode catalyst materials.
Modeling Electrical Conductivity of Injection-Molded Polymer Composite Bipolar Plates
Authors: Trimpey Jonathan K , Myers Maxwell T , Beevers David B , Bakis Charles E , Hollinger Adam S
Published: September 2024

Bipolar plates can be responsible for up to 40% of the total stack cost and 80% of the weight of a polymer electrolyte membrane fuel cell. To reduce these cost and weight limitations, this work explores modeling and injection molding of polymer composites. A fiber contact model was developed to predict electrical conductivity based upon direction in the material, fiber length and diameter, fiber resistivity, fiber volume fraction, and fiber angle of alignment. Fiber alignment was measured experimentally by imaging cross sections of injection-molded nylon/nickel-coated carbon fiber (NiCF) composites. Composites were molded with NiCF loadings ranging from 5 to 40 wt%. Up to 15 wt%, modeling predictions show good correlation with experimental conductivity measurements. Samples with at least 15 wt% NiCF exceeded the United States Department of Energy technical target for bipolar plate conductivity (>100 S/cm), reaching 250 S/cm.
Advances in Fuel Cell Performance Using Simulation Analysis in Toshiba Energy Systems & Solutions Corporation
Authors: Takamata Hikaru , Shimotori Soichiro , Hidai Shoichi , Yamashita Kyohei
Published: September 2024

The influence of channel and rib width of bi-polar plates on gas diffusion performance was investigated by simulation and experimental measurement. Simulation results showed that a ch./rib ratio of about 2 is a compromise between diffusivity and resistance, and that higher performance can be expected. The advanced cell with bi-polar plates with this flow channel geometry was fabricated and its performance was evaluated. IV characteristics of advanced cell exceeded simulation results, indicating that the effect of improved GDL/MPL tortuosity on diffusion performance was greater than expected.
Numerical Modeling of Water Transport in a Microporous Layer-Coated Porous Transport Layer for a Polymer Electrolyte Membrane Water Electrolyzer with an Interdigitated Flow Field for Internal Gas-Liquid Separation
Authors: Nakajima Hironori , Bolay Linda , Ekström Henrik , Shima Asuka , Lindbergh Göran , Sone Yoshitsugu
Published: September 2024

A novel design for interdigitated flow fields in polymer electrolyte membrane electrolyzers has been developed for both ground and space applications. This design separates oxygen and liquid water internally, eliminating the need for water circulators to remove bubbles and external gas-liquid separators with buoyancy. The capillary pressure in the hydrophobic microporous layer (MPL) of the anode porous transport layer facilitates internal separation of oxygen gas and pressurized liquid water. A finite element model (COMSOL Multiphysics) simulates water transport in the MPL, while electrochemical impedance spectra determine the electrochemical kinetic parameters for the model. The model takes into account the oxygen bubble coverage of the cathode, liquid water saturation in the MPL, and the current ratio between liquid water and water vapor at the MPL-cathode layer interface. The vapor from liquid water in the MPL is modeled to mix with oxygen for diffusion. A volumetric water evaporation rate as a linear function of liquid water saturation in the MPL is assumed, where the rate constant is estimated from vapor permeation tests.
Applied Metal Hydride System Optimization to Improve Hydrogen Fuel Cell System Performance in Mobile Heavy-Duty Applications
Authors: Kordel Markus , Radler Dominik
Published: September 2024

Hydrogen fuel cell vehicles face challenges in competing against battery electric systems as their efficiency is 25 % lower. Especially in the heavy-duty sector the efficiency of fuel cell electric vehicles needs to be increased accordingly, as this market will play a major role in future. One promising approach could be to decrease the energy demand of refrigerated trucks by the pressure energy between the hydrogen tank and fuel cell in metal hydrides to provide cooling power. However, the cooling power output is not constant and further efficiency improvements can be done. Here we show a simulative state space controller optimization which can provide a constant power output and can increase the efficiency by 8 % points compared to an uncontrolled system. A future combination with state-of-the-art efficiency improvement measures can potentially increase the system efficiency even further.
Electrodeposition of Ti in molten AF–ACl–A3TiF6 (A = Li, Na, K)
Authors: Norikawa Yutaro , Nohira Toshiyuki
Published: September 2024

Electrochemical behaviors of Ti(III) ions and electrodeposition of Ti were investigated in molten AF–ACl–A3TiF6 (A = Li, Na, K) at 973 K. Redox currents corresponding to Ti(III)/Ti(0) and Ti(IV)/Ti(III) reactions were observed by cyclic voltammetry. The redox potentials of the reactions with reference to Cl2/Cl− and F2/F−
　were most positive for the Li system, followed by the Na system, and most negative for the K system. The differences in the potential can be explained by the interactions of alkali cations and F- ions; smaller cations interact more strongly with F−, resulting in a weaker interaction between Ti(III) ions and F- ions. As a result, the electrochemical stability of TiF6
3− decreased. The electrodeposited Ti was confirmed to be crystalline by XRD, and the orientation of the Ti crystals differed depending on the molten salt.