Institute of Electrical Engineering

A precision measurement by the Alpha Magnetic Spectrometer on the International Space Station of the positron fraction in primary cosmic rays in the energy range from 0.5 to 350 GeV based on 6.8 × 10(6) positron and electron events is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to ∼ 250 GeV, but, from 20 to 250 GeV, the slope decreases by an order of magnitude. The positron fraction spectrum shows no fine structure, and the positron to electron ratio shows no observable anisotropy. Together, these features show the existence of new physical phenomena.

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Abstract With the enormous development of the electric vehicle market, fast charging battery technology is highly required. However, the slow kinetics and lithium plating under fast charging condition of traditional graphite anode hinder the fast charging capability of lithium‐ion batteries. To develop anode materials with rapid Li‐ions diffusion capability and fast reaction kinetics has received widely attentions. This review summarizes the current status in the exploration of fast charging anode materials, mainly including the critical challenge of achieving fast charging capability, the inherent structures and lithium storage mechanisms of various anode materials, as well as the recent progress to improve the rate performance involving morphology regulation, structure design, surface/interface modification, as well as forming multiphase systems. Finally, the challenges and future directions of developing fast charging Li‐ion batteries are highlighted.

Information processing during human cognitive and emotional operations is thought to involve the dynamic interplay of several large-scale neural networks, including the fronto-parietal central executive network (CEN), cingulo-opercular salience network (SN), and the medial prefrontal-medial parietal default mode networks (DMN). It has been theorized that there is a causal neural mechanism by which the CEN/SN negatively regulate the DMN. Support for this idea has come from correlational neuroimaging studies; however, direct evidence for this neural mechanism is lacking. Here we undertook a direct test of this mechanism by combining transcranial magnetic stimulation (TMS) with functional MRI to causally excite or inhibit TMS-accessible prefrontal nodes within the CEN or SN and determine consequent effects on the DMN. Single-pulse excitatory stimulations delivered to only the CEN node induced negative DMN connectivity with the CEN and SN, consistent with the CEN/SN's hypothesized negative regulation of the DMN. Conversely, low-frequency inhibitory repetitive TMS to the CEN node resulted in a shift of DMN signal from its normally low-frequency range to a higher frequency, suggesting disinhibition of DMN activity. Moreover, the CEN node exhibited this causal regulatory relationship primarily with the medial prefrontal portion of the DMN. These findings significantly advance our understanding of the causal mechanisms by which major brain networks normally coordinate information processing. Given that poorly regulated information processing is a hallmark of most neuropsychiatric disorders, these findings provide a foundation for ways to study network dysregulation and develop brain stimulation treatments for these disorders.

Full-cell cycling of a high density silicon-majority anode with 2× volumetric capacity of graphite and a stabilized coulombic efficiency exceeding 99.9%.

Precision measurements by the Alpha Magnetic Spectrometer on the International Space Station of the primary cosmic-ray electron flux in the range 0.5 to 700 GeV and the positron flux in the range 0.5 to 500 GeV are presented. The electron flux and the positron flux each require a description beyond a single power-law spectrum. Both the electron flux and the positron flux change their behavior at ∼30 GeV but the fluxes are significantly different in their magnitude and energy dependence. Between 20 and 200 GeV the positron spectral index is significantly harder than the electron spectral index. The determination of the differing behavior of the spectral indices versus energy is a new observation and provides important information on the origins of cosmic-ray electrons and positrons.

A precision measurement by AMS of the positron fraction in primary cosmic rays in the energy range from 0.5 to 500 GeV based on 10.9 million positron and electron events is presented. This measurement extends the energy range of our previous observation and increases its precision. The new results show, for the first time, that above ∼200 GeV the positron fraction no longer exhibits an increase with energy.

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Multi-junction (tandem) solar cells (TSCs) consisting of multiple light absorbers with considerably different band gaps show great potential in breaking the Shockley-Queisser (S-Q) efficiency limit of a single junction solar cell by absorbing light in a broader range of wavelengths. Perovskite solar cells (PSCs) are ideal candidates for TSCs due to their tunable band gaps, high PCE up to 25.2%, and easy fabrication. PSCs with high PCEs are typically fabricated via a low temperature solution method, which are easy to combine with many other types of solar cells like silicon (Si), copper indium gallium selenide (CIGS), narrow band gap PSCs, dye-sensitized, organic, and quantum dot solar cells. As a matter of fact, perovskite TSCs have stimulated enormous scientific and industrial interest since their first development in 2014. Significant progress has been made on the development of perovskite TSCs both in the research laboratories and industrial companies. This review will rationalize the recent exciting advancement in perovskite TSCs. We begin with the introduction of the historical development of TSCs in a broader context, followed by the summary of the state-of-the-art development of perovskite TSCs with various types of device architectures. We then discuss the strategies for improving the PCEs of perovskite TSCs, including but not limited to the design considerations on the transparency of perovskite absorbers and metal electrodes, protective layers, and recombination layers (RLs)/tunnel junctions (TJs), with a particular focus on the band gap tuning and thickness adjustment of active layers. We subsequently introduce a range of measurement techniques for the characterization of perovskite TSCs. We also cover other core issues related to the large-scale applications and commercialization. Finally, we offer our perspectives on the future development of emerging photovoltaic technologies as the device performance enhancement and cost reduction are central to almost any type of solar cell applied in the perovskite TSCs.

A high-strength poly(vinyl alcohol) chemical hydrogel (PCH) film is prepared by coupling covalent crosslinking with a film-casting process. Conducting polyaniline (PANI) is then embedded in the PCH film by in situ growth to form a composite film with a PANI-hydrogel-PANI configuration, which leads to a new conceptual flexible supercapacitor with all-in-one configuration that exhibits superior electrochemical performance and mechanical flexibility.

Abstract High‐temperature capability is critical for polymer dielectrics in the next‐generation capacitors demanded in harsh‐environment electronics and electrical‐power applications. It is well recognized that the energy‐storage capabilities of dielectrics are degraded drastically with increasing temperature due to the exponential increase of conduction loss. Here, a general and scalable method to enable significant improvement of the high‐temperature capacitive performance of the current polymer dielectrics is reported. The high‐temperature capacitive properties in terms of discharged energy density and the charge–discharge efficiency of the polymer films coated with SiO 2 via plasma‐enhanced chemical vapor deposition significantly outperform the neat polymers and rival or surpass the state‐of‐the‐art high‐temperature polymer nanocomposites that are prepared by tedious and low‐throughput methods. Moreover, the surface modification of the dielectric films is carried out in conjunction with fast‐throughput roll‐to‐roll processing under ambient conditions. The entire fabrication process neither involves any toxic chemicals nor generates any hazardous by‐products. The integration of excellent performance, versatility, high productivity, low cost, and environmental friendliness in the present method offers an unprecedented opportunity for the development of scalable high‐temperature polymer dielectrics.

The enumeration of rare circulating epithelial cells (CEpCs) in the peripheral blood of metastatic cancer patients has shown promise for improved cancer prognosis. Moving beyond enumeration, molecular analysis of CEpCs may provide candidate surrogate endpoints to diagnose, treat, and monitor malignancy directly from the blood samples. Thorough molecular analysis of CEpCs requires the development of new sample preparation methods that yield easily accessible and purified CEpCs for downstream biochemical assays. Here, we describe a new immunomagnetic cell separator, the MagSweeper, which gently enriches target cells and eliminates cells that are not bound to magnetic particles. The isolated cells are easily accessible and can be extracted individually based on their physical characteristics to deplete any cells nonspecifically bound to beads. We have shown that our device can process 9 mL of blood per hour and captures >50% of CEpCs as measured in spiking experiments. We have shown that the separation process does not perturb the gene expression of rare cells. To determine the efficiency of our platform in isolating CEpCs from patients, we have isolated CEpCs from all 47 tubes of 9-mL blood samples collected from 17 women with metastatic breast cancer. In contrast, we could not find any circulating epithelial cells in samples from 5 healthy donors. The isolated CEpCs are all stored individually for further molecular analysis.

New-generation integrated devices based on dye-sensitized and perovskite solar cells for energy harvesting and storage are significantly important for self-powering systems and portable/wearable electronics.

Most modern microprocessors employ one or two levels of on-chip caches in order to improve performance. These caches are typically implemented with static RAM cells and often occupy a large portion of the chip area. Not surprisingly, these caches often consume a significant amount of power. In many applications, such as portable devices, low power is more important than performance. We propose to trade performance for power consumption by filtering cache references through an unusually small L1 cache. An L2 cache, which is similar in size and structure to a typical L1 cache, is positioned behind the filter cache and serves to reduce the performance loss. Experimental results across a wide range of embedded applications show that the filter cache results in improved memory system energy efficiency. For example, a direct mapped 256-byte filter cache achieves a 58% power reduction while reducing performance by 21%, corresponding to a 51% reduction in the energy-delay product over a conven...

A precision measurement by AMS of the antiproton flux and the antiproton-to-proton flux ratio in primary cosmic rays in the absolute rigidity range from 1 to 450 GV is presented based on $3.49\ifmmode\times\else\texttimes\fi{}1{0}^{5}$ antiproton events and $2.42\ifmmode\times\else\texttimes\fi{}1{0}^{9}$ proton events. The fluxes and flux ratios of charged elementary particles in cosmic rays are also presented. In the absolute rigidity range $\ensuremath{\sim}60$ to $\ensuremath{\sim}500\text{ }\text{ }\mathrm{GV}$, the antiproton $\overline{p}$, proton $p$, and positron ${e}^{+}$ fluxes are found to have nearly identical rigidity dependence and the electron ${e}^{\ensuremath{-}}$ flux exhibits a different rigidity dependence. Below 60 GV, the ($\overline{p}/p$), ($\overline{p}/{e}^{+}$), and ($p/{e}^{+}$) flux ratios each reaches a maximum. From $\ensuremath{\sim}60$ to $\ensuremath{\sim}500\text{ }\text{ }\mathrm{GV}$, the ($\overline{p}/p$), ($\overline{p}/{e}^{+}$), and ($p/{e}^{+}$) flux ratios show no rigidity dependence. These are new observations of the properties of elementary particles in the cosmos.

The Alpha Magnetic Spectrometer (AMS) is a precision particle physics detector on the International Space Station (ISS) conducting a unique, long-duration mission of fundamental physics research in space. The physics objectives include the precise studies of the origin of dark matter, antimatter, and cosmic rays as well as the exploration of new phenomena. Following a 16-year period of construction and testing, and a precursor flight on the Space Shuttle, AMS was installed on the ISS on May 19, 2011. In this report we present results based on 120 billion charged cosmic ray events up to multi-TeV energies. This includes the fluxes of positrons, electrons, antiprotons, protons, and nuclei. These results provide unexpected information, which cannot be explained by the current theoretical models. The accuracy and characteristics of the data, simultaneously from many different types of cosmic rays, provide unique input to the understanding of origins, acceleration, and propagation of cosmic rays.

The identification of mutations in genes that cause human diseases has largely been accomplished through the use of positional cloning, which relies on linkage mapping. In studies of rare diseases, the resolution of linkage mapping is limited by the number of available meioses and informative marker density. One recent advance is the development of high-density SNP microarrays for genotyping. The SNP arrays overcome low marker informativity by using a large number of markers to achieve greater coverage at finer resolution. We used SNP microarray genotyping for homozygosity mapping in a small consanguineous Israeli Bedouin family with autosomal recessive Bardet-Biedl syndrome (BBS; obesity, pigmentary retinopathy, polydactyly, hypogonadism, renal and cardiac abnormalities, and cognitive impairment) in which previous linkage studies using short tandem repeat polymorphisms failed to identify a disease locus. SNP genotyping revealed a homozygous candidate region. Mutation analysis in the region of homozygosity identified a conserved homozygous missense mutation in the TRIM32 gene, a gene coding for an E3 ubiquitin ligase. Functional analysis of this gene in zebrafish and expression correlation analyses among other BBS genes in an expression quantitative trait loci data set demonstrate that TRIM32 is a BBS gene. This study shows the value of high-density SNP genotyping for homozygosity mapping and the use of expression correlation data for evaluation of candidate genes and identifies the proteasome degradation pathway as a pathway involved in BBS.

This paper presents a comprehensive survey on acquisition, tracking, and pointing (ATP) mechanisms used in free-space optical (FSO) communications systems. ATP mechanisms are a critical component for a wide variety of use cases of mobile FSO communications. ATP mechanisms are used to align an FSO transmitter and receiver to attain line-of-sight, which is required for effective operation of FSO communications. Transceiver motion is not only associated to mobile stations but also to temporary displacements experienced by stationary FSO terminals, such as in building-to-building FSO communications. This survey categorizes ATP mechanisms according to their working principles, use cases, and implementation technology. This paper also discusses advantages and disadvantages of the surveyed ATP mechanisms, and presents a discussion on challenges and future research.

Iron with a large magnetic moment was widely believed to be harmful to the emergence of superconductivity because of the competition between the static ordering of electron spins and the dynamic formation of electron pairs (Cooper pairs). Thus, the discovery of a high critical temperature ( T c ) iron-based superconductor (IBSC) in 2008 was accepted with surprise in the condensed matter community and rekindled extensive study globally. IBSCs have since grown to become a new class of high- T c superconductors next to the high- T c cuprates discovered in 1986. The rapid research progress in the science and technology of IBSCs over the past decade has resulted in the accumulation of a vast amount of knowledge on IBSC materials , mechanisms, properties, and applications with the publication of more than several tens of thousands of papers. This article reviews recent progress in the technical applications (bulk magnets, thin films , and wires) of IBSCs in addition to their fundamental material characteristics. Highlights of their applications include high-field bulk magnets workable at 15–25 K, thin films with high critical current density ( J c ) > 1 MA/cm 2 at ∼10 T and 4 K, and an average J c of 1.3 × 10 4 A/cm 2 at 10 T and 4 K achieved for a 100-m-class-length wire. These achievements are based on the intrinsically advantageous properties of IBSCs such as the higher crystallographic symmetry of the superconducting phase, higher critical magnetic field, and larger critical grain boundary angle to maintain high J c . These properties also make IBSCs promising for applications using high magnetic fields.

This article focuses on the problem of prescribed-time control for a class of uncertain nonlinear systems. First, a prescribed-time stability theorem is proposed by following the adaptive technology for the first time. Based on this theorem, a new state feedback control strategy is put forward by using the backstepping method for high-order nonlinear systems with unknown parameters to ensure the prescribed-time convergence. Moreover, the prescribed-time controller is obtained in the form of continuous time-varying feedback, which can render all system states converge to zero within the prescribed time. It should be noted that the prescribed time is independent of system initial conditions, which means that the prescribed time can be set arbitrarily within the physical limitations. Finally, two simulation examples are provided to illustrate the effectiveness of our proposed algorithm.