Performance and potential capabilities of thermionic conversion devices

The power ratings of wind energy conversion systems (WECS) are increasing considerably due to high demand on wind power. Thus, multilevel power converters are becoming an interesting solution in the largest WECS, especially the three-level neutral-point-clamped (3L-NPC) thanks to its simple implementation and proper performance compared to other topologies. However, the main drawback of the 3L-NPC is that the power losses are unevenly distributed among the switching devices, limiting its output power capability. Current literature focuses on the three-level active neutral-point-clamped (3L-ANPC) as an evolution of the 3L-NPC, enabling a more even power loss distribution. However, in the 3L-ANPC there are still some devices suffering from both large switching and conduction power losses. Thus, this paper proposes new design guidelines for a 3L-ANPC inverter to force that each device mainly withstands either switching or conduction power losses. Then, the most suitable device is selected for each position, enabling a significant improvement in power loss distribution, thermal performance, converter efficiency and output power capability. A 2 MW low-voltage WECS is simulated with an electro-thermal model developed in PLECS, reaching a reduction of around 25% in power losses, a reduction of 50% in maximum junction temperature increase above ambient temperature, a reduction of 75% in maximum junction temperature variation, and an increase of around 85% in converter output power rating, compared to the conventional 3L-NPC and the 3L-ANPC.

Experimental study of the hydrodynamic performance of a U-oscillating water column wave energy converter

With the increasing functions in digital circuit, flexibility and energy-efficiency play important roles in addressing future mobile/cloud computing systems. Scaling of CMOS devices and interconnects has contributed to high performance and low power operation of ULSI devices. Due to excessive stand-by power accompanying device shrinking, further scaling is experiencing serious roadblocks, and in near future, scaling will face a physical limit of the device dimension. One of the solutions to enhance device performance without scaling is to introduce “More than Moore” devices, which are integrated on CMOS without increasing the chip-size. Especially, resistive switching devices, such as magnetic random-access memory [1], phase-change memory [2], and electrochemical switch [3-5], have attracted much attention because of their potential for use in not only memory but also logic application.Atom switch is an electrochemical resistive-change device categorized in the cation type [4]. The electrochemical phenomenon is nonvolatile and based on electrolysis of the Cu electrode to produce a precipitation of Cu between the electrodes, which realizing a high ON/OFF conductance ratio. Previously, we reported a replacement of the SRAM-based switch with atom switch integrated in Cu-BEOL (Fig.2) [6]. An elimination of the forming process and high ON/OFF-state reliabilities have been realized by introducing a polymer solid-electrolyte (PSE) [7], a complementary atom switch (CAS) [8] and alloy electrodes [9].As compared to a two-terminal device, a three-terminal device is advantageous for the logic application since the separation of the programming line and signal transfer line simplifies circuit design and reduces the layout area. In this paper, a three-terminal resistive-change device featuring the resistive-change junctions coupled with the diode-inserted gate is discussed. References R. Nebashi, et al., “A 90nm 12ns 32Mb 2T1MTJ MRAM”, IEEE Solid-State Circuits Conference - Digest of Technical Papers, 8-12 Feb. 2009 Page(s):462 - 463,463a. D. Ielmini, et al., “Reliability Impact of Chalcogenide-Structure Relaxation in Phase-Change Memory (PCM) Cells—Part I: Experimental Study”,IEEE Trans. Electron Devices, vol. 56, no. 5, pp. 1070-1077, 2009.M. N. Kozicki, et al., “Applications of programmable resistance changes in metal-doped chalcogenides”, Pennington NJ USA: Electrochem. Soc. 298–309 (1999).T. Sakamoto, et al., “Nanometer-scale switches using copper sulfide”, Appl. Phys. Lett.82, 3032, (2003).R. Waser and M. Aono, “Nanoionics-based resistive switching memories”, Nature Material, vol.6, pp. 833-839 (2007).M. Tada, et al., “Nonvolatile Crossbar Switch using TiOx/TaSiOy Solid-electrolyte”, IEEE Transactions on Electron Devices, vol. 57, no.8, pp.1987-1995, (2010).M. Tada, et al.,“Polymer Solid-Electrolyte (PSE) Switch Embedded on CMOS for Nonvolatile Crossbar Switch”, IEEE Transactions on Electron Devices, vol. 58, no. 12, pp.4398-4405, (2011).M. Tada, et al.,“Improved Off-state Reliability of Nonvolatile Resistive Switch with Low Programming Voltage”, IEEE Transactions on Electron Devices, vol. 59, no. 9, pp.2357-2362, (2012).M. Tada, et al.,“Improved On-state Reliability of Atom Switch Using Alloy Electrodes”, IEEE Transactions on Electron Devices, vol. 60, no. 10, pp.3534-3540, (2013).

Processing optimization, mechanical properties, corrosion behavior and cytocompatibility of additively manufactured Zn-0.7Li biodegradable metals

Previous studies involving whole-body post-mortem human surrogates (PHMS) have generated biomechanical response specifications for physically simulated accelerative loading intended to reproduce seat and floor velocity histories occurring in under-body blast (UBB) events (e.g.,. References 10, 11, 21 These previous studies employed loading conditions that only rarely produced injuries to the foot/ankle and pelvis, which are body regions of interest for injury assessment in staged UBB testing using anthropomorphic test devices. To investigate more injurious whole-body conditions, three series of tests were conducted with PMHS that were equipped with military personal protective equipment and seated in an upright posture. These tests used higher velocity and shorter duration floor and seat inputs than were previously used with the goal of producing pelvis and foot/ankle fractures. A total of nine PMHS that were approximately midsize in stature and mass were equally allocated across three loading conditions, including a 15.5m/s, 2.5ms time-to-peak (TTP) floor velocity pulse with a 10m/s, 7.5ms TTP seat pulse; a 13m/s, 2.5ms TTP floor pulse with a 9.0m/s, 5ms TTP seat pulse; and a 10m/s, 2.5ms TTP floor pulse with a 6.5m/s, 7.5ms TTP seat pulse. In the first two conditions, the seat was padded with a ~ 120-mm-thick foam cushion to elongate the pulse experienced by the PMHS. Of the nine PMHS tests, five resulted in pelvic ring fractures, five resulted in a total of eight foot/ankle fractures (i.e.,two unilateral and three bilateral fractures), and one produced a femur fracture. Test results were used to develop corridors describing the variability in kinematics and in forces applied to the feet, forces applied to the pelvis and buttocks in rigid seat tests, and in forces applied to the seat foam in padded seat tests. These corridors and the body-region specific injury/no-injury response data can be used to assess the performance and predictive capability of anthropomorphic test devices and computational models used as human surrogates in simulated UBB testing.

India bears a high burden of acute coronary syndrome, with younger patients and a high prevalence of ST-elevation myocardial infarction (STEMI). Spandan is, therefore, an attractive smartphone-based electrocardiogram (ECG) device that could allow for potentially early diagnosis as well as enabling timely intervention which may even save lives in resource-poor settings. The study aimed to assess the performance and diagnostic capability of the Spandan smartphone-based ECG device in decision-making for percutaneous coronary intervention (PCI) by analyzing the initial ST-segment elevation, which was compared to a 12-lead ECG as the gold standard (BPL Cardiart ECG Machine). This was an observational cross-sectional study involving 184 eligible participants with chest pain presenting to the local hospital, in Meerut, Uttar Pradesh, India. The study was conducted for the evaluation of the diagnostic appropriateness of the Spandan ECG device for the detection of ST elevation as compared to standard 12-lead ECGs so that the cardiologists could be more easily guided in their decisions relative to PCI. Patients with the onset of chest pain within or after 120 h and ST elevation above 1 mm in two or more leads were enrolled and patients with dementia, bundle branch block, cardiogenic shock, and ECG artifacts were excluded. The analysis included calculating response characteristics and estimating correlation coefficients and confusion matrix to compare both appraisal methods. The Spandan device performed with good agreement with the gold standard ECG, particularly in the leads II, III, and AVF, with Pearson correlation coefficients close to 1. The ST elevation in the Spandan device showed no statistical difference compared to the 12-lead ECG. The device exhibited a sensitivity of 94% and a positive predictive value of 94% for ST-elevation detection, thus having supportive evidence for possible usefulness for decision-making in PCI. ECG findings, such as that of the smartphone-based device (Spandan Pro ECG, a single channel autoswitched ECG machine), demonstrated comparable accuracy with the gold standard 12-lead ECG for the diagnosis of ST elevation and helped in making clinical decisions in patients requiring PCI, especially in resource-limited settings.

In the past five years, rapid progress has been achieved in thermionic conversion devices. The lifetime of experimental devices has been extended from a few hundred hours to over ten thousand hours. Overall efficiencies of over 14% have been measured on several devices at temperatures consistent with practical heat sources. Reproducibility of devices has been improved greatly as evidenced by the construction and testing of several large batches of similar converters. Hardware devices intended to fit the envelopes and restraints of specific systems have been designed and are now under development. Preliminary results achieved during these developmental efforts are quite promising. Although recent progress has been encouraging, much work remains to make thermionic conversion devices useful as real system components. Converter designs must be matched better to overall power system parameters and heat sources. The reproducibility of converters must be investigated in more detail to determine the present state of the art and to formulate requirements for improved processing techniques. More life-testing under well simulated environments must be done on hardware devices designed to fit system needs. This paper will review the progress achieved in experimental and hardware devices. The problems that were solved in achieving this progress will be discussed. A description will also be presented of the problems remaining to achieve practical thermionic hardware.

The purpose of this study is to examine the influence of entrepreneurial orientation and social capital on innovation and performance capabilities in achieving competitive advantage of small and medium enterprises (SMEs). SMEs contribute significantly to the Indonesian economy, especially in the event of a monetary crisis. Some research on performance and innovation capabilities in SMEs that have been done so far have focused mainly on finance, operation and marketing aspects but have not explored the intangible assets such as entrepreneurial and social capital.Intangible assets become key success factor in improving the performance of SMES, especially in the era of ASEAN Economic Community 2016. The method used in this research is descriptive and explanatory.The sample in this study are owners of SMEs handicraft in Semarang, Jepara, Kudus, with as many as 254 respondents. Sampling is conducted on SMEs that have been operating for at least five years, having employees over 10 people and still exist to this date. Data were collected using survey method through closed and open questionnaire and interview. Data analysis was done by using structural equation model with AMOS program.The results show that there is a significant influence between entrepreneurship orientation and social capital on innovation and performance capabilities. Innovation capability has a significant influence on performance improvement and competitive advantage of SMEs.

AlGaN/GaN high-electron-mobility transistors (HEMTs) for applications in radiation environments has required the exact determination of their radiation hardness. Although bulk GaN is the preferred substrate for the epitaxial growth of GaN and AlGaN, (111) silicon is a possible substrate for HEMT devices. The stability of electrical parameters of enhancement-mode (E-mode) GaN HEMTs under gamma irradiation is an essential characterization for reliability. The present work reports the transfer characteristics degradation of E-mode GaN HEMTs under various total dose irradiation from 5krad up to 60Mrads. This represents the first comprehensive total dose study ranging from a few krads up the tens of Mrads. The measured device-to-device variations within groups of devices are presented. The evolutions of critical DC parameters with accumulated total dose is found to be significant at low doses and saturates at high dose levels. The degradation mechanism is very similar to the reported radiation-induced shallow electron traps that trap and release electrons in the near surface GaN and AlGaN layers. Due to the unique properties including high breakdown voltage, high electron mobility and high thermal stability, wide-bandgap semiconductor power electronic devices, especially Gallium Nitride (GaN) high-electron-mobility transistors (HEMTs), have shown great promise in space, defense and nuclear applications, which often involve radiation-hardened electronics that require high radiation tolerance to fluxes of neutrons or gamma ray of devices. To turn the promising potential of GaN HEMTs into reality, investigations on the influence of irradiation on the device performance and reliability are essential. Many studies have investigated the radiation hardness of group III–nitride compound semiconductor devices under various irradiation types, such as electrons, protons, neutrons, and X-rays and at various total irradiation doses. They generally showed higher radiation tolerance compared with Si because of high displacement energy of GaN, demonstrating the favorability of GaN devices in hard radiation environments. Many studies have investigated the influence of 60Co gamma radiation on the device electrical characteristics. However, they were all focusing on depletion mode (D-mode) devices. Enhancement mode (E-mode) GaN-on-Si transistors have been commercially available for years. Their major advantages over D-mode devices are elimination of negative voltage supply and the enabling of direct-coupled FET logic (DCFL) for digital circuits. They also improve the efficiency of commercial DC-DC converters in various power levels and topologies. A previous work on gamma radiation of E-mode GaN-on-Si HEMTs only reported cumulative total doses of up to 1 Mrads (Si). The present work provides a complete coverage of low-to-high irradiation doses from 5krads up to 60Mrads (Si), for commercially available E-mode GaN HEMTs and the devices are characterized to gauge variations in the critical DC parameters. To the best of the author’s knowledge, the present work is the first to investigate the gamma radiation tolerance of E-mode GaN HEMTs covering such a wide range of total doses. This facilitates the observation of the complete degradation behavior of DC parameters in hard radiation applications of the E-mode GaN HEMTs. The devices were supplied in the form of 0.9mm square passivated die with round solder bumps for contacts. They have a rated continuous drain-to-source voltage VDS of 60V, and a rated continuous drain current ID of 1A. These GaN-on-Si devices were fabricated on Si wafers considering process compatibility and cost. An aluminum nitride (AlN) thin layer was grown on the Si wafer to be a seed layer for the AlGaN/GaN heterostructure. Subsequently, the AlGaN/GaN heterostructure was grown on the AlN layer, with a thin AlGaN layer grown above the highly resistive GaN serving as a strained interface between the GaN and AlGaN crystal layers, allowing the creation of a two-dimensional electron gas (2DEG) filled with abundant free electrons with ultra-high mobility. The gate electrode was processed subsequently forming a depletion region under the gate. As an E-mode transistor, the device is turned on by applying a positive bias to the gate. All the irradiations were conducted at room temperature by 60Co gamma-rays with a flux of 318.5Rads (Si)/s, at the dry-cell panoramic gamma irradiator in the University of Maryland Radiation Facilities. The entire irradiation procedure consists of two parts. The first part is higher-dose irradiation with total doses of up to 60Mrads based on two stages. At the first stage, the devices were irradiated at 10Mrads, while at the second stage, the devices were irradiated for another 50Mrads, with three of them taken out after 25Mrads during the second stage. The second part is lower-dose irradiations with total doses of up to 2Mrads. The temperature throughout the irradiation process was monitored to be below 30°C.

Industrial processes which use induction and dielectric heating are still relying on resonant converters based on vacuum tubes. New emerging medium‐voltage silicon carbide (SiC) semiconductor power devices have a potential to replace vacuum tubes and allow for more efficient and compact converters in the high‐frequency range. High‐voltage packages have been proposed in the literature that are suitable for the 10 kV SiC metal–oxide–semiconductor field‐effect transistors (MOSFETs), and its fast voltage switching capabilities in hard‐switched applications have been demonstrated. However, no packaging is presented which allows the high‐frequency operation of a 10 kV SiC MOSFET die. This study proposes the design of a power module for MHz resonant operation of a 10 kV SiC MOSFET. At high switching frequencies, the gate losses become substantial, thus the gate driver is included inside the power module package to ensure a low inductive and high thermally conductive design as seen from the gate driver. The inductance of the proposed power module layout structure is evaluated using ANSYS Q3D Extractor. The thermal performance of the integrated gate‐driver circuitry is experimentally verified. Finally, the resonant operation of a medium‐voltage SiC MOSFET power module is demonstrated experimentally at 1 MHz.

A reduction of development costs will have a significant impact on the total cost of the vacuum electron devices. Experimental testing cycles can be reduced or eliminated through the use of simulation‐based design methodology, thereby reducing the time and cost of development. Moreover, by use of modern optimization tools for automating the process of seeking specific solution parameters and for studying dependencies of performance on parameters, new performance capabilities can be achieved, without resorting to expensive cycles of hardware fabrication and testing. Simulation‐based‐design will also provide the basis for sensitivity studies for determining the manufacturing tolerances associated with a particular design. Since material properties can have a critical effect on the performance of the vacuum electron devices, the design tools require precise knowledge of material characteristics, such as dielectric properties of the support rods, loss profile etc. Sensitivity studies must therefore include the effects of materials properties variation on device performance. This will provide insight for choosing the proper technological processes in order to achieve these tolerances, which is of great importance for achieving cost reduction. A successful design methodology depends on the development of accurate and efficient design tools with predictive capabilities. These design tools must be based on realistic models capable of high fidelity representation of geometry and materials, they must have optimization capabilities, and they must be easy to use.

Motion and performance of BBDB OWC wave energy converters: I, hydrodynamics

Data converters significantly contribute to efficient and accurate data processing in Internet of Things (IoT) systems. As IoT expands into agriculture, industrial automation, and healthcare (AIH), precise and low-power data conversion has become crucial to support longer battery life and reliable performance in IoT devices. Efficient data converters are key to reducing energy use, especially in components like comparator circuits, which consume significant energy in successive approximation register analog-to-digital converters (SAR ADCs). This survey provides an in-depth review of recent developments in low-power data converter design, examining techniques that help reduce power consumption at various stages. It emphasizes advancements, such as energy scaling, dynamic voltage references, and architectural optimizations that enhance efficiency without compromising performance. A specific analysis of emerging technology trends, such as the application of machine learning in data converter design, is explored to stimulate further innovation. Machine learning (ML)-based optimization, including adaptive calibration, noise reduction, and real-time performance optimization, presents new opportunities for enhancing efficiency and accuracy while addressing critical design constraints in IoT applications. While quantum encryption offers promising advancements in securing IoT data transmission, a broader security perspective beyond encryption is necessary, including concerns, such as attack detection and data integrity, ensuring the robustness of IoT systems. This review also examines latency, signal integrity, and accuracy issues, offering a roadmap for next-generation converter designs and reducing power consumption in data converters, which are fundamental to enhancing the performance and lifespan of IoT devices.

This quantitative study sought to identify the performance capabilities and competencies that organizations in the northern midwestern United States expect of future performance improvement professionals at the undergraduate and graduate levels. Eighty-nine performance improvement professionals representing 89 organizations completed an online survey that captured the participants' perspective regarding undergraduate and graduate-level performance capabilities, and undergraduate competency expectations. Results suggest that participants expect several training and development performance capabilities, a few organization developments, and no performance management performance capabilities at the undergraduate level. Several training and development capabilities, most organization development capabilities, and all performance management performance capabilities were expected at the graduate level. This definition is fundamental to support academic curricular development and the field of performance improvement.

Nanostructures provide a simple, effective, and low-cost route to enhance the light-trapping capability of optoelectronic devices. In recent years, nano-optical structures have been widely used in perovskite optoelectronic devices to greatly enhance the device performance. However, the inherent instability of perovskite materials hinders the practical application of these nanostructured optoelectronic devices. Here, in situ encapsulated moiré lattice perovskite photodetectors (PDs) by two nanograting-structured soft templates with relative rotation angles is fabricated. The confinement growth of the two nanograting templates leads to crystal growth with moiré lattice structure, which improves the light-harvesting ability of the perovskite crystal, thereby improving the device performance. The PDexhibits responsivity to 1026.5AW-1 . The Moiré lattice-perovskite-based PD maintained 95% of the initial performance after 223days. After being continuously sprayed with water moist for 180min, the performance is maintained at 95.7% of its initial level. The nanograting structure endows the device with high polarization sensitivity of Imax /Imin as high as 9.1.