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Achieving long‐term device stability is one of the most challenging issues that impede the commercialization of perovskite solar cells (PSCs). Recent studies have emphasized the significant role of the cathode interfacial layer (CIL) in determining the stability of inverted p‐i‐n PSCs. However, experimental investigations focusing on the influence of the CIL on PSC degradation have not been systematically carried out to date. In this study, a comparative analysis was performed on the PSC device stability by using four different CILs including practical oxides like ZnO and TiOx. A new implemented co‐doping approach was found to results in high device performance and enhanced device stability. The PSC with a thick film configuration of chemically modified TiOx CIL preserves over 77 % of its initial efficiencies of 17.24 % for 300 h under operational conditions without any encapsulation. The PSCs developed are among the most stable reported for methylammonium lead iodide (MAPbI3) perovskite compositions., In for the CIL: Highly stable inverted perovskite solar cells (PSCs) are assembled by using chemically modified titanium suboxide (TiOx) as the cathode interfacial layer (CIL). Codoping enhances the electrical properties of the TiOx CIL, providing better inner encapsulation with thick film configuration. The PSCs exhibit significantly improved operational stability, maintaining >77 % of their initial efficiencies for up to 300 h without encapsulation.

An experimental investigation into the nonlinear optical properties of rhenium diselenide (ReSe2) was conducted at a wavelength of 1.9 μm using the open-aperture and closed-aperture Z-scan techniques for the nonlinear optical coefficient (β) and nonlinear refractive index (n2) of ReSe2, respectively. β and n2 measured at 1.9 μm were ~ − 11.3 × 103 cm/GW and ~ − 6.2 × 10–2 cm2/GW, respectively, which to the best of our knowledge, are the first reported measurements for ReSe2 in the 1.9-μm spectral region. The electronic band structures of both ReSe2 and its defective structures were also calculated via the Perdew–Becke–Erzenhof functional to better understand their absorption properties. A saturable absorber (SA) was subsequently fabricated to demonstrate the usefulness of ReSe2 for implementing a practical nonlinear optical device at 1.9 μm. The 1.9-μm SA exhibited a modulation depth of ~ 8% and saturation intensity of ~ 11.4 MW/cm2. The successful use of the ReSe2-based SA for mode-locking of a thulium–holmium (Tm–Ho) co-doped fiber ring cavity was achieved with output pulses of ~ 840 fs at 1927 nm. We believe that the mode-locking was achieved through a hybrid mechanism of saturable absorption and nonlinear polarization rotation.

Metallic 2D materials can be promising saturable absorbers for ultrashort pulsed laser production in the long wavelength regime. However, preparing and manipulating their 2D structures without layer stacking have been nontrivial. Using a combined experimental and theoretical approach, we demonstrate here that a metallic titanium carbide (Ti3C2Tx), the most popular MXene 2D material, can have excellent nonlinear saturable absorption properties even in a highly stacked state due to its intrinsically existing surface termination, and thus can produce mode-locked femtosecond pulsed lasers in the 1.9-μm infrared range. Density functional theory calculations reveal that the electronic and optical properties of Ti3C2Tx MXene can be well preserved against significant layer stacking. Indeed, it is experimentally shown that 1.914-μm femtosecond pulsed lasers with a duration of 897 fs are readily generated within a fiber cavity using hundreds-of-layer stacked Ti3C2Tx MXene saturable absorbers, not only being much easier to manufacture than mono- or few-layered ones, but also offering character-conserved tightly-assembled 2D materials for advanced performance. This work strongly suggests that as-obtained highly stacked Ti3C2Tx MXenes can serve as superb material platforms for versatile nanophotonic applications, paving the way toward cost-effective, high-performance photonic devices based on MXenes.

The thickness of the film produced by spin coating is different from the theoretically calculated thickness based on the Newtonian fluid equation. In this study, the rotational time and rotational speed (in revolutions per minute [RPM]) were used as the control parameters, and the thickness differences between the actual and theoretical results were analyzed based on statistical analyses. Furthermore, we investigated the effects of the aging time (i.e., time after spin coating before heat treatment curing) independently from the parameters of the theoretical equation for spin coating of Newtonian fluids mentioned above. The thickness of the film formed by the spin coater within a period of 300 s was smaller than the theoretically predicted thickness at all rotation speeds irrespective of aging. Based on statistical analyses of the measured thickness values, we confirmed that rotational speeds in the range of 2000–6000 RPM within a period of 300 s did not yield thickness differences owing to aging time. However, below 1500 RPM, the thickness without aging time was smaller than the thickness with aging time. In addition, the thicknesses of the edge and center of the substrate were unequal but became uniform as the aging time increased. Additionally, the estimated thickness based on the constructed plots yielded completely different results from those predicted by the existing equation about Newtonian fluids. Based on the analyses of the thickness as a function of aging time and speed, we confirmed that the aging time—which was not accounted for in the conventional equation—was the parameter that primarily affected the thickness.

With the increasing demands of indoor air quality monitoring, highly sensitive and selective gas sensor arrays consisting of metal oxide semiconductors have been increasingly studied. As an effective strategy to obtain the desired performance, noble metal functionalization is frequently chosen owing to its target-specific sensing mechanisms. However, the lack of a comprehensive analysis on the sensing mechanisms of different combinations of metal oxides and noble metals limit the versatility of these sensor arrays for use in selective gas sensor arrays. In this study, we fabricate a 3 × 3 gas sensor array to obtain a reliable comparison of the sensing mechanism through the use of three metal oxides—WO3, SnO2 and NiO—in three different nanostructure forms: a thin film and dome-like nanostructures with and without Au nanoparticle (NP) decoration. The responses of the sensor arrays to four target gases (CH3COCH3, C6H5CH3, NH3, and H2S) are generally enhanced by the dome-like nanostructure and show distinctively enhanced responses when the sensors are decorated with Au NPs. Moreover, the dome-like SnO2 with Au NPs shows an increase of up to 121 times for C6H5CH3 compared with the pristine SnO2 thin film. Additionally, the sensitization effects of Au NPs depend on the types of metal oxides and gases, which improve the gas discrimination capability by diversifying the gas selectivity of the sensor units in the array. The prepared sensor array can distinguish four target gases by principal component analysis (PCA). The contributions of different enhancement mechanisms, which are dependent on the gases and metal oxides, are investigated by comparing the activation energy of each gas response with and without Au. The comparison among the chosen gases reveals that the decoration of Au NPs is effective for C6H5CH3 and NH3 regardless of the type of metal oxide. Among the metal oxides, the effects of Au NPs on gas responses are in the order of SnO2, NiO, and WO3, in which the energy level difference between the Au NPs and metal oxide are 0.2, 0.1, and −0.6 eV, respectively. These results confirm that the dominant enhancement mechanism of Au NPs for each combination of gases and metal oxide is a decrease in activation energy. Therefore, this study provides a systematic understanding of the sensitization mechanism of Au NPs on metal oxides toward gases for the fabrication of selective gas sensor arrays.

Virtual power plant (VPP) technologies continue to develop to embrace various types of distributed energy resources (DERs) that have inherent real-time uncertainty. To prevent side effects on the power system owing to the uncertainty, the VPP should manage its internal resources’ uncertainty as a whole. This paper proposes an optimal operation strategy for a VPP participating in day-ahead and real-time energy market so that a distributed energy resource aggregation (DERA) can cope with real-time fluctuation due to uncertainties while achieving its maximum profit. The proposed approach has bidding models of the DERAs including microgrid, electric vehicle aggregation, and demand response aggregation, as well as the VPP. The VPP determines internal prices applied to the DERA by evaluating its real-time responses to the day-ahead schedule and updating proposed pricing function parameters, and the DERA adjusts its energy reserves. By repeating this coordination process, the VPP can establish an optimal operation strategy to manage real-time uncertainty on the DERA’s own. The effectiveness of the proposed strategy is verified by identifying a capability of the DERA to cope with real-time fluctuation through scenario-based simulations. The result shows that the VPP can reduce 1.6% of cost while the internal price applied to the DERA is close to the maximum.

Amine-containing polyelectrolytes such as polyethyleneimine (PEI) are commonly used as cathode interfacial materials (CIMs); however, they are rarely found in non-fullerene acceptor (NFA) organic solar cells due to undesirable chemical reactions between PEI and NFAs. Unveiling the nature of these chemical interactions and developing chemically stable amine-containing polyelectrolytes is inevitable for achieving highly efficient and stable NFA organic solar cells. Herein, the reaction between PEI and 2-(3-oxo-2,3-dihydro-1H-inden-1-ylidene)malononitrile (INCN)-based NFAs was investigated using a model system. 15N-isotope labeling experiments and 2D nuclear magnetic resonance (NMR) studies revealed that the products were generated by the Michael addition reaction and existed as the keto–enol tautomers. Based on the identified undesirable reaction, we developed a series of functionalized PEIs that are compatible with INCN-based NFAs by protecting the reactive amine functional groups. Highly efficient and stable NFA organic solar cells were successfully fabricated by the use of functionalized PEIs with broad work function tunability and improved chemical stability, which led to NFA organic solar cells with high power conversion efficiency (PCE) values of over 15% and thermally stable device operation for more than 360 hours at 100 °C.

Various redox-active organic molecules can serve as ideal electrode materials to realize sustainable energy storage systems. Yet, to be more appropriate for practical use, considerable architectural engineering of an ultrathick, high-loaded organic electrode with reliable electrochemical performance is of crucial importance. Here, by utilizing the synergetic effect of the non-covalent functionalization of highly conductive non-oxidized graphene flakes (NOGFs) and introduction of mechanically robust cellulose nanofiber (CNF)-intermingled structure, a very thick (≈ 1 mm), freestanding organic nanohybrid electrode which ensures the superiority in cycle stability and areal capacity is reported. The well-developed ion/electron pathways throughout the entire thickness and the enhanced kinetics of electrochemical reactions in the ultrathick 5,10-dihydro-5,10-dimethylphenazine/NOGF/CNF (DMPZ-NC) cathodes lead to the high areal energy of 9.4 mWh·cm−2 (= 864 Wh·kg−1 at 158 W·kg−1). This novel ultrathick electrode architecture provides a general platform for the development of the high-performance organic battery electrodes.

We report the first investigation results of the nonlinear optical properties of As2Te3. More specifically, the nonlinear optical absorption properties of the prepared α-As2Te3 were investigated at wavelengths of 1.56 and 1.9 μm using the open-aperture (OA) Z-scan technique. Using the OA Z-scan technique, the nonlinear absorption coefficients (β) of α-As2Te3 were estimated in a range from (− 54.8 ± 3.4) × 104 cm/GW to (− 4.9 ± 0.4) × 104 cm/GW depending on the irradiance of the input beam at 1.56 μm, whereas the values did from (− 19.8 ± 0.8) × 104 cm/GW to (− 3.2 ± 0.1) × 104 cm/GW at 1.9 μm. In particular, the β value at 1.56 μm is an order of magnitude larger than the previously reported values of other group-15 sesquichalcogenides such as Bi2Se3, Bi2Te3, and Bi2TeSe2. Furthermore, this is the first time report on β value of a group-15 sesquichalcogenide at a 1.9-μm wavelength. The density functional theory (DFT) calculations of the electronic band structures of α-As2Te3 were also conducted to obtain a better understanding of their energy band structure. The DFT calculations indicated that α-As2Te3 possess sufficient optical absorption in a wide wavelength region, including 1.5 μm, 1.9 μm, and beyond (up to 3.7 μm). Using both the measured nonlinear absorption coefficients and the theoretically obtained refractive indices from the DFT calculations, the imaginary parts of the third-order optical susceptibilities (Im χ(3)) of As2Te3 were estimated and they were found to vary from (− 39 ± 2.4) × 10–19 m2/V2 to (− 3.5 ± 0.3) × 10–19 m2/V2 at 1.56 μm and (− 16.5 ± 0.7) × 10–19 m2/V2 to (− 2.7 ± 0.1) × 10–19 m2/V2 at 1.9 μm, respectively, depending on the irradiance of the input beam. Finally, the feasibility of using α-As2Te3 for SAs was investigated, and the prepared SAs were thus tested by incorporating them into an erbium (Er)-doped fiber cavity and a thulium–holmium (Tm–Ho) co-doped fiber cavity for both 1.5 and 1.9 μm operation.

MoO3 has potential advantages in price and weight over more widely studied WO3 for electrochromic devices, but it typically suffers from inferior electrochromic performance. Here, it is demonstrate...

Recent breakthroughs in molecular design have allowed for remarkable achievement in the field of non-fullerene acceptor (NFA)-based organic solar cells (OSCs) with high power conversion efficiencies (PCEs) of over 15%. However, despite such promising advances, the inferior stability of OSCs under operating conditions remains a prominent challenge that must be overcome for their practical realization. Here, versatile ternary photoactive systems with simultaneously enhanced efficiency and photostability are developed by introducing a small amount of fullerene (PC71BM) into a narrow band gap NFA-based bulk heterojunction nanocomposite (PTB7-Th:IEICO-4F); this approach leads to an enhanced PCE of 10.55% and a prolonged lifetime, retaining approximately 80% of the initial PCE after 500 h of operation under continuous illumination. Based on the energy levels and surface energies of the component materials, cascade energetic alignment facilitates electron transfer without trapping. The PTB7-Th/PC71BM interface provides an energy barrier to suppress recombination between holes in PTB7-Th and electrons in IEICO-4F. Moreover, a small amount of PC71BM promotes favorable molecular packing and orientation of IEICO-4F, leading to enhanced electron mobility and balanced charge transport. A study using transient absorption spectroscopy reveals that the ternary blend effectively suppresses the evolution of charge recombination.

The ternary chalcogenide, ZnIn2S4, is known to exhibit various polymorphic expressions: from the cubic spinel phase to various polytypic layered hexagonal structures, commonly known as α, β, IIa, a...

Background Chuna Manual Therapy (CMT) has been widely used in Korea, and coverage in Korean National Health Insurance (NHI) was finally implemented in 2019. The objectives of this study were to analyze the process of NHI coverage for CMT qualitatively, and to summarize important roles, streams, and implications regarding its inclusion in the modern public health insurance system. Methods Related literature was collected and 8 key personnel involved in the policy-making process were qualitatively interviewed, and Zahariadis’ version of the Multiple Streams Framework (MSF) was applied to analyze the policy agenda setting and the roles of stakeholders. Results Through the collaborative efforts of various stakeholders, a pilot coverage project for CMT was implemented in 2017, and coverage was expanded nationwide in 2019. MSF showed that it was mainly achieved through three streams: governmental change (political stream), demand from the general public and KM doctors (problem stream), and strengthening/reinforcement of the feasibility and acceptability of the policy (policy steam). Also, the roles of policy entrepreneurs and resulting changes were shown to be significant for the overall process. Conclusion NHI coverage for CMT was realized through collective policy and research efforts from the government and academic sectors. The roles of stakeholders were shown to be significant in the overall process, and documentation of their involvement is hoped to be of use of other countries that utilize traditional and/or manual medicine.

We design a simulator in order to seek a surface warship’s survivability against a torpedo attack using MATLAB GUI. Assuming that a torpedo chases a warship in an acoustic-homing way, we mo...

An efficient method for the formation of hexagonal disk shape C60 crystals at desired positions on a solid substrate has been achieved. The detailed growth behavior was studied through in-situ observation and series of control experiments. Our position selective growth technique enabled a fabrication of bottom electrode type C60 single crystal devices which exhibited n-type field-effect transistor behavior and photo response. Moreover, the C60 single crystal devices were further exploited to study alkali metal doped C60 crystal and its superconductivity.

Editor’s note: Debug and validation are important steps required to ensure that systems-on-chip satisfies the design specs. This article presents an elegant diagnosis technique integrated within the network-on-chip infrastructure. The authors demonstrate the proposed technique on an FPGA prototype. —Umit Y. Ogras, Arizona State University

In recent years, three-dimensional (3-D) printing has presented a new manufacturing paradigm and attracted considerable attention since it allows for products to be fabricated as solid objects by printing successive layers of material following instructions produced through computer-aided design. Here, for the first time, the 3-D printing technology based on fused deposition modeling is demonstrated to be readily useful in the fabrication of a fiberized saturable absorber (SA) intended for use in ultrafast mode-locking of an all-fiberized laser. The fiberized SA was fabricated on a side polished fiber platform by printing a low-cost composite of graphene and polylactic acid (PLA). The insertion loss and modulation depth of the fabricated SA were measured to be ∼3.8 and 1.2 dB, respectively. The saturation power and the modulation depth for the transverse electric (TE) mode were estimated to be ∼16 W and ∼2.2% , respectively, while the values for the transverse magnetic (TM) mode were ∼24 W and ∼1.5%, respectively. Using the fabricated SA in an erbium fiber ring cavity, stable femtosecond soliton pulses was readily produced at 1560.2 nm. To the best of the authors’ knowledge this is the first experimental demonstration using 3-D printing technology to implement a fiberized saturable absorber.

Here, we have examine the efficacy of bis[3-(triethoxysilyl)propyl]tetrasulfide (Si69) for physic-chemical recycling of waste rubber tyre (WRT) at two different operating temperatures (i.e., 170 °C and 190 °C). The reclaimed rubbers (RR) have been used to fabricate devices similar to the single electrode triboelectric nanogenerator (SETNG) to realize its future applicability. Sol content, crosslink density, Moony viscosity, and rheology of the RR samples have been investigated to understand the effect of operating temperatures on the reclamation (alias regeneration) process. Although very low content of Si69 (i.e., 1g) reclaims the WRT at both the temperatures, with increasing the concentration (i.e., ≥ 3g), it shows coupling behavior (i.e., re-vulcanization) at 190 °C and reclaiming behavior (i.e., de-vulcanization) at 170 °C. Hot-pressing at 170 °C and 190 °C reproduced the similar observations. SETNG made of RR at 170 °C produced more output voltage than that of the 190 °C, and exhibits distinct tactile sensation towards different objects viz., human finger, latex rubber glove, cotton glove and PTFE sheet. The tactile sensing capability is further visualized by exploiting the principal component analysis (PCA). This work represents a low-cost, low-temperature, time-resolved way for regeneration of eco-hazard waste rubber and its future applicability towards development of tactile sensing materials, energy harvester, etc. Also, the response of TNG can be utilized to know the degree of regeneration.

In pursuit of the elusive mechanism of high-TC superconductors (HTSC), spectroscopic imaging scanning tunneling microscopy (SI-STM) is an indispensable tool for surveying local properties of HTSC. ...

Providing a high quality video streaming experience in a mobile data network via the ubiquitous HTTP Adaptive Streaming (HAS) protocol is challenging. This is largely because HAS traffic arrives as regular Internet Protocol (IP) packets, indistinguishable from those of other data services. This paper presents real-time network-based Machine Learning (ML) classifiers incurring low overhead and capable of (a) detecting the service type of different flows including HAS, and (b)detecting the player status for users with HAS flows. We utilize random forests , an ensemble classifier, relying only upon standard unencrypted packet headers. By applying the ML classifier outputs to derive scheduling metrics, we show how existing LTE base-station schedulers can improve video Quality-of-Experience (QoE) while incurring minimal overhead. For a simulated LTE cellular network, we present quantitative performance results that include misclassification errors. Our classification and scheduling framework is shown to provide an improved video QoE with tolerable impact on other non-video best effort services. These design insights can be applied to optimize video delivery in current and future wireless networks.

미 트럼프 행정부는 2018년 5월 24일 상업적 우주활동을 촉진하기 위한 규제개혁방향을 담은 우주정책명령 SPD-2(Space Policy Directive-2)를 발표하고, 뒤이어 6월 18일 우주상황 관리 정책에 관한 행정명령 SPD-3를 발표했다. 이 행정명령은 주요 우주 분야에 대한 개 혁조치를 담고 있는데, 이 정책은 2017년 6월 재구성된 국가우주위원회(National Space Council: NSC)가 성안한 개혁 권고안을 대통령이 승인한 것으로 연방정부의 강력한 개혁추진을 위한 가이던스를 제공한다. 상업우주활동개혁정책은 앞서 2017년 12월 18일 발표된 국가안보전략(National Security Strategy)의 큰 틀에서 경제적 번영과 국가안보를 동시에 달성하기 위한 노력으로 이해할 수 있다. 상업적 우주활동을 촉진함으로써 미국의 국익을 달성하고자 하는 미국의 정책과 입법은 우주활동을 규율하는 우주조약을 위반한다는 우려와 논란을 불러일으킬 수 있다. 이에 국제사회는 미국의 상업우주개혁정책에서 노정되는 법적 쟁점에 대한 국제적 논의를 통해 우주기술의 발전과 상업화 진전에 맞는 보편적 국제규범을 형성하기 위한 노력을 가속화해야 한다.

In this paper, we present GradPIM, a processing-in-memory architecture which accelerates parameter updates of deep neural networks training. As one of processing-in-memory techniques that could be realized in the near future, we propose an incremental, simple architectural design that does not invade the existing memory protocol. Extending DDR4 SDRAM to utilize bank-group parallelism makes our operation designs in processing-in-memory (PIM) module efficient in terms of hardware cost and performance. Our experimental results show that the proposed architecture can improve the performance of DNN training and greatly reduce memory bandwidth requirement while posing only a minimal amount of overhead to the protocol and DRAM area., Accepted to HPCA 2021

This study reports a Q-switching-based, 2058-nm holmium (Ho) fiber laser incorporating a saturable absorber (SA) based on graphene oxide (GO). The SA was prepared with a side-polished fiber, while GO particles were deposited onto the fiber-polished surface to realize an all-fiber SA. A continuous-wave thulium-doped all-fiber laser, which was configured with a master-oscillator power-amplifier (MOPA) structure, was constructed as a pumping source. By inserting the fabricated SA into an all-fiber ring resonator based on 1-m length of Ho-doped fiber, Q-switched pulses could readily be obtained at a wavelength of 2058 nm. The pulse width was observed to vary from 2.01 to 1.56 &mu, s as the pump power was adjusted from ~759 to 1072 mW, while the repetition rate was tunable from 45.56 to 56.12 kHz. The maximum values of average optical power and pulse energy were measured as ~11.61 mW and 207.05 nJ, respectively, at a ~1072 mW pump power.

Much of what is known about high-temperature cuprate superconductors stems from studies based on two surface analytical tools, angle-resolved photoemission spectroscopy (ARPES) and spectroscopic imaging scanning tunneling microscopy (SI-STM). A question of general interest is whether and when the surface properties probed by ARPES and SI-STM are representative of the intrinsic properties of bulk materials. We find this question is prominent in thin films of a rarely studied cuprate DBCO. We synthesize DBCO films by oxide molecular beam epitaxy and study them by in situ ARPES and SI-STM. Both ARPES and SI-STM show that the surface DBCO layer is different from the bulk of the film. It is heavily underdoped, while the doping level in the bulk is close to optimal doping evidenced by bulk-sensitive mutual inductance measurements. ARPES shows the typical electronic structure of a heavily underdoped CuO2 plane and two sets of one-dimensional bands originating from the CuO chains with one of them gapped. SI-STM reveals two different energy scales in the local density of states, with one corresponding to the superconductivity and the other one to the pseudogap. While the pseudogap shows large variations over the length scale of a few nanometers, the superconducting gap is very homogeneous. This indicates that the pseudogap and superconductivity are of different origins.

One of the well‐known strategies for achieving high‐performance light‐activated gas sensors is to design a nanostructure for effective surface responses with its geometric advances. However, no study has gone beyond the benefits of the large surface area and provided fundamental strategies to offer a rational structure for increasing their optical and chemical performances. Here, a new class of UV‐activated sensing nanoarchitecture made of highly periodic 3D TiO2, which facilitates 55 times enhanced light absorption by confining the incident light in the nanostructure, is prepared as an active gas channel. The key parameters, such as the total 3D TiO2 film and thin‐shell thicknesses, are precisely optimized by finite element analysis. Collectively, this fundamental design leads to ultrahigh chemoresistive response to NO2 with a theoretical detection limit of ≈200 ppt. The demonstration of high responses with visible light illumination proposes a future perspective for light‐activated gas sensors based on semiconducting oxides., The high‐performance light‐activated NO2 gas sensors using 3D TiO2 nanostructures are achieved by the unique light harvesting properties of the nanoporous structures. The light scattering effects from optical maze‐like nanostructures and numerous intermediate energy states from atomic layer deposition of the film electronically activate 3D TiO2 and enhance its gas sensing performance under UV illumination.

Recently, smart home construction based on Internet-of-Thing (IoT) has been actively performed, and smart devices including various sensors have been used for building a smart home. Many sensors in a smart home collect specific data, collect them in a central server and provide smart home residents or organically manage smart homes by combining them with artificial intelligence. However, each sensor transmits data to a central server, resulting in power consumption, which leads to a reduction in energy efficiency.In this paper, we propose an Adaptive Sensor Data Transmission Scheduling Scheme that schedules data transmission interval based on the data variation of each sensor. The proposed scheme reduces the total amount of data transmission by classifying the class adaptively according to the amount of data measured in the sensor of the device and excluding unnecessary data transmission. As a result, the proposed scheme reduces power for exchanging data between various devices and the central server.

This paper presents an efficient way of 2D reprojection method of 3D voxel data which is generated from multiple 2D image sources. In order to minimize the image quality degradation generated by postprocessing such as hole filling, A 2D reprojection method using gaussian aggregation of voxel attribute intensity is proposed. Proposed method efficiently removes generation of holes while maintaining graceful intensity of projected 2D image planes, which can finally reconstruct original 2D source images with less quality degradation.

We propose FlexReduce, an efficient and flexible all-reduce algorithm for distributed deep learning under irregular network hierarchies. With ever-growing deep neural networks, distributed learning over multiple nodes is becoming imperative for expedited training. There are several approaches leveraging the symmetric network structure to optimize the performance over different hierarchy levels of the network. However, the assumption of symmetric network does not always hold, especially in shared cloud environments. By allocating an uneven portion of gradients to each learner (GPU), FlexReduce outperforms conventional algorithms on asymmetric network structures, and still performs even or better on symmetric networks.

We propose a novel method for training neural networks to predict the future prices of stock indexes. Unlike previous works, we do not use target stock index data for training neural networks for index prediction. Instead, we use only the data of individual companies to obtain sufficient amount of data for training neural networks for stock index prediction. As a result, our method can avoid various problems due to training complex machine learning models on a small amount of data. We performed numerous types of experiments to test methods designed for predicting the future price of the S&P 500 which is one of the most commonly traded stock indexes. Our experiments show that neural networks trained using our method outperform neural networks trained on stock index data. Compared with other state-of-the-art methods, our method is conceptually simpler and easier to apply, and achieves better results. We obtained approximately a 5-16% annual return before transaction costs during the test period (2006-2018).

We demonstrate the implementation of a temperature sensor based on mechanically induced long period fiber gratings (MILPFGs) using a 3-D printer. The temperature sensitivities are measured to be –97 pm/°C and 0.33 dB/°C, respectively.

Significance By making a variety of quantitative comparisons between electronic visualization experiments and a theory describing coexisting pair density wave and superconductive states in cuprates, we find striking correspondence throughout. Our model can thus explain the microscopic origins of many key atomic-scale phenomena of the cuprate broken-symmetry state. These observations are consistent with the possibility that a short-range pair density wave (PDW) state coexists with superconductivity below a critical hole density in Bi2Sr2CaCu2O8, that the charge density wave modulations in cuprates are a consequence of the PDW state, that the cuprate pseudogap is the antinodal gap of the PDW, and that the critical point in the cuprate phase diagram occurs due to disappearance of the PDW., The defining characteristic of hole-doped cuprates is d-wave high temperature superconductivity. However, intense theoretical interest is now focused on whether a pair density wave state (PDW) could coexist with cuprate superconductivity [D. F. Agterberg et al., Annu. Rev. Condens. Matter Phys. 11, 231 (2020)]. Here, we use a strong-coupling mean-field theory of cuprates, to model the atomic-scale electronic structure of an eight-unit-cell periodic, d-symmetry form factor, pair density wave (PDW) state coexisting with d-wave superconductivity (DSC). From this PDW + DSC model, the atomically resolved density of Bogoliubov quasiparticle states Nr,E is predicted at the terminal BiO surface of Bi2Sr2CaCu2O8 and compared with high-precision electronic visualization experiments using spectroscopic imaging scanning tunneling microscopy (STM). The PDW + DSC model predictions include the intraunit-cell structure and periodic modulations of Nr,E, the modulations of the coherence peak energy Δpr, and the characteristics of Bogoliubov quasiparticle interference in scattering-wavevector space q-space. Consistency between all these predictions and the corresponding experiments indicates that lightly hole-doped Bi2Sr2CaCu2O8 does contain a PDW + DSC state. Moreover, in the model the PDW + DSC state becomes unstable to a pure DSC state at a critical hole density p*, with empirically equivalent phenomena occurring in the experiments. All these results are consistent with a picture in which the cuprate translational symmetry-breaking state is a PDW, the observed charge modulations are its consequence, the antinodal pseudogap is that of the PDW state, and the cuprate critical point at p* ≈ 19% occurs due to disappearance of this PDW.

To best leverage high-bandwidth storage and network technologies requires an improvement in the speed at which we can decompress data. We present a “refine and recycle” method applicable to LZ77-type decompressors that enables efficient high-bandwidth designs and present an implementation in reconfigurable logic. The method refines the write commands (for literal tokens) and read commands (for copy tokens) to a set of commands that target a single bank of block ram, and rather than performing all the dependency calculations saves logic by recycling (read) commands that return with an invalid result. A single “Snappy” decompressor implemented in reconfigurable logic leveraging this method is capable of processing multiple literal or copy tokens per cycle and achieves up to 7.2GB/s, which can keep pace with an NVMe device. The proposed method is about an order of magnitude faster and an order of magnitude more power efficient than a state-of-the-art single-core software implementation. The logic and block ram resources required by the decompressor are sufficiently low so that a set of these decompressors can be implemented on a single FPGA of reasonable size to keep up with the bandwidth provided by the most recent interface technologies.

Wavelength-selective harvesting by organic solar cells (OSCs) has attracted significant research attention due to the unique potential of these materials for smart photovoltaic window applications. Here, a visibly transparent OSC is demonstrated by utilizing both near-infrared (NIR)-absorbing polymer donor and nonfullerene acceptor (NFA) materials with narrow optical band gaps of less than 1.4 eV. Despite the substantial overlap in absorption spectra between the donor and acceptor, sufficient lowest unoccupied molecular orbital (LUMO) and highest occupied molecule orbital (HOMO) energy offsets for efficient charge separation with concurrent very low voltage losses yield a power conversion efficiency (PCE) of 9.13%. Moreover, with the introduction of an ultrathin Ag film (8 nm) as a transparent top electrode, semitransparent OSCs exhibit an excellent dual-side photovoltaic performance of 5.7 and 3.9% under bottom and top illumination, respectively, with high transmittance reaching 60% at wavelengths from 400 to 600 nm. This approach is expected to provide a new perspective in developing the highly efficient and transparent OSCs.

Optic-disc photography (ODP) has proven to be very useful for optic nerve evaluation in glaucoma. In real clinical practice, however, limited patient cooperation, small pupils, or media opacities can limit the performance of ODP. The purpose of this study was to propose a deep-learning approach for increased resolution and improved legibility of ODP by contrast, color, and brightness compensation. Each high-resolution original ODP was transformed into two counterparts: (1) down-scaled 'low-resolution ODPs', and (2) 'compensated high-resolution ODPs' produced via enhancement of the visibility of the optic disc margin and surrounding retinal vessels using a customized image post-processing algorithm. Then, the differences between these two counterparts were directly learned through a super-resolution generative adversarial network (SR-GAN). Finally, by inputting the high-resolution ODPs into SR-GAN, 4-times-up-scaled and overall-color-and-brightness-transformed 'enhanced ODPs' could be obtained. General ophthalmologists were instructed (1) to assess each ODP's image quality, and (2) to note any abnormal findings, at 1-month intervals. The image quality score for the enhanced ODPs was significantly higher than that for the original ODP, and the overall optic disc hemorrhage (DH)-detection accuracy was significantly higher with the enhanced ODPs. We expect that this novel deep-learning approach will be applied to various types of ophthalmic images.

We investigate the recovery-time impact of a saturable-absorber on mode-locking performance of a fiber laser. The recovery-time was found to have a significant impact in a fiber cavity with normal GVD rather than anomalous GVD. © 2020 The Author(s)

Morphology-retained solid-state photoconversion of anthracene (AN) to 9,10-anthraquinone (PC-ANQ) and dipara-anthracene (PC-DPA) was accomplished by irradiating mercury lamp light to plate-shaped AN single crystal in oxygen and argon atmosphere, respectively. The photoconverted crystals retained the original plate shape morphology of the starting AN crystal, whereas the emission profile and crystal structure were significantly changed. The electrical conductivity of PC-ANQ crystal is 5 orders of magnitude greater than that of the starting AN crystal, whereas the PC-DPA crystal exhibits a decreased conductivity. The AN/PC-ANQ/PC-DPA heterostructures with smooth interface were successfully obtained by inducing the photoconversion only at the desired area.

Increasing the open circuit voltage (Voc) is one of the key strategies for further improvement of the efficiency of perovskite solar cells. It requires fundamental understanding of the complex optoelectronic processes related to charge carrier generation, transport, extraction and their loss mechanisms inside a device upon illumination. Herein we report the important origin of Voc losses in methylammonium lead iodide perovskite (MAPI) based solar cells, which results from undesirable positive charge (hole) accumulation at the interface between the perovskite photoactive layer and the PEDOT:PSS hole transport layer. We show strong correlation between the thickness-dependent surface photovoltage and device performance, unraveling that the interfacial charge accumulation leads to charge carrier recombination and results in a large decrease in Voc for the PEDOT:PSS/MAPI inverted devices (180 mV reduction in 50-nm-thick device compared to 230-nm-thick one). In contrast, accumulated positive charges at the TiO2/MAPI interface modify interfacial energy band bending, which leads to an increase in Voc for the TiO2/MAPI conventional devices (70 mV increase in 50-nm-thick device compared to 230-nm-thick one). Our results provide an important guideline for better control of interfaces in perovskite solar cells to improve device performance further.

An atomically thin two-dimensional (2D) covalent organic framework (COF) was successfully synthesized via the photon-assisted imine condensation reaction within 1 h from the highly uniform and homogeneous precursor solution layer floating on the water surface. The polarity optimization of the precursor solution was the key step for the successful formation of the high-quality 2D COF because only the precursor solution consisting of polarity-controlled solvents allows ideal floating on the water surface. The polarity-controlled solution not only prohibits the agglomeration of the organic precursors on the water surface but also facilitates the wafer scale and layer number-controllable synthesis of the 2D COF. The resulting 2D COF has a uniform porous structure and highly oriented layered structure along the out-of-plane direction as observed by microscopy analysis and X-ray diffraction, respectively. In addition, we successfully fabricated field effect transistor type polyimine-based COF (pi-COF) electronic devices to demonstrate the prompt electrical responses to photo-exposure and water vapor exposure, suggesting the potential applications of the pi-COF in electrical photodetector or moisture-detector devices.

In this paper, we report an efficient alkali metal doping system for organic single crystals. Our system employs an enhanced diffusion method for the introduction of alkali metal into organic single crystals by controlling the sample temperature to induce secondary thermal activation. Using this system, we achieved intercalation of potassium into picene single crystals with closed packed crystal structures. Using optical microscopy and Raman spectroscopy, we confirmed that the resulting samples were uniformly doped and became K2picene single crystal, while only parts of the crystal are doped and transformed into K2picene without secondary thermal activation. Moreover, using a customized electrical measurement system, the insulator-to-semiconductor transition of picene single crystals upon doping was confirmed by in situ electrical conductivity and ex situ temperature-dependent resistivity measurements. X-ray diffraction studies showed that potassium atoms were intercalated between molecular layers of picene, and doped samples did not show any KH- nor KOH-related peaks, indicating that picene molecules are retained without structural decomposition. During recent decades, tremendous efforts have been exerted to develop high-performance organic semiconductors and superconductors, whereas as little attention has been devoted to doped organic crystals. Our method will enable efficient alkali metal doping of organic crystals and will be a resource for future systematic studies on the electrical property changes of these organic crystals upon doping.

This paper proposes an evolved Self-Adaptive Interactive Navigation Tool (SAINT+) to reduce the delivery time of emergency services and to improve navigation efficiency for the vehicles influenced by accidents. To the best of our knowledge, SAINT+ is the first attempt to optimize the delivery of emergency services as well as the navigation routes of vehicles around accident areas. Based on the congestion contribution model of SAINT and aggregated information from vehicles in the vehicular cloud, we propose a virtual path reservation strategy for emergency vehicles to guarantee a fast emergency service delivery. We also develop an accident area protection scheme based on an adjusted congestion contribution matrix and protection zones to evacuate vehicles in the accident area. To further reduce travel delay of neighbor vehicles in the accident area, we also present a dynamic traffic flow control model. Through extensive simulations with a real-world map, SAINT+ outperforms other state-of-the-art schemes for the travel delay of emergency vehicles. In scenarios with a high vehicle density, SAINT+ reduces the travel delay of emergency vehicles by 42.2%.

The era of the Internet of Things (IoT) is upon us. In this era, minimizing power consumption becomes a primary concern of system-on-chip designers. Ultralow power (ULP) very large-scale integration circuits have been receiving considerable interest from both academia and industry as the best-suited techniques for IoT devices, which can take full advantage of power-saving that voltage scaling potentially achieves. Consequently, research on ULP designs has begun to yield tangible outcomes, namely ULP circuits. However, little attention has been paid to ULP network-on-chip (NoC), although the NoC is an essential of the ULP chips, and its power consumption accounts for a significant portion of the total power. This paper focuses on ULP NoCs, and presents a new power management method that exploits delay versus temperature characteristics of ULP circuits. Recent studies on ULP circuits show that delay versus temperature characteristics are fundamentally different from normal circuits, i.e., the delay of the ULP circuits implemented in state-of-the-art bulk CMOS operating at low supply voltages or in FinFET technologies decreases with increasing temperature, a phenomenon known as the temperature effect inversion (TEI). Starting with an intuition that at a certain temperature point, power savings without performance penalty can be achieved by increasing the router frequency to create the opportunity to turn off some routers in ULP NoCs, or by decreasing the NoC supply voltage level, an optimization method is presented to maximize the power savings with minor performance penalty. To validate the proposed method, a concrete ULP NoC simulator, TEI-Noxim, has been developed. Experimental results demonstrate that TEI-aware NoC achieves an average of 36.0% power reduction over 21 applications.

Elimination of charge trapping at defects is highly challenging for poly-crystalline organometal halide perovskites. Here, we report a new architecture for reinforcing the built-in electric field (Ein) across the photoactive layer with a pair of strong electric dipole layers (EDLs). The paired EDLs significantly intensify the Ein across the perovskite layer, resulting in suppressed charge trapping of photogenerated charges. As a result, our low-temperature processed P–I–N planar PeSC devices using the paired EDLs exhibit a higher power conversion efficiency (ηmax ∼ 19.4%) and a smaller device-to-device variation with a standard deviation (S.D.) of 0.70%, which far surpass those (ηmax ∼ 17.8%, S.D. ∼ 1.1%) of the devices with typical charge transport layers.

Here we report on the development of thin film manufacturing processes based on new and sustainable green solutions. We focused on utilizing green based surface solutions. The peroxo titanium complex (PTC) solution-based thin film fabrication method used does not require additional heat treatment and complex processes to remove organic matter. Conditions suitable for thin film fabrication were derived through optimization of precursor concentration and reaction temperature. As a result of I-V test of TiN/TiO2/FTO samples fabricated by applying this technology, it has been proven that it can operate as a resistive random-access memory (RRAM). The measured I-V curve suggests that TiN/TiO2/FTO RRAM exhibits bipolar resistive switching (RS) characteristics through the formation of oxygen vacancy (Vo) filament conduction paths. We also used the double logarithmic plot analysis to confirm that the dominant conduction mechanism of the device is the space charge limited conduction (SCLC) model.

Nanostructured Si is a promising material for photoelectrochemical water splitting, but it has the problem of being well oxidized in water. Depositing a TiO2 layer on the Si surface is an effective way to protect it from oxidation and increase light absorption. However, the lattice mismatch between Si and TiO2 acts as a defect that causes an efficiency reduction. To improve the interface and electrical properties of TiO2/Si, nitric acid oxidation of Si (NAOS) is used to form a high-density SiO2 layer and analyze the effect of photoelectrochemical properties. Due to the lattice mismatch, the TiO2/Si sample (−3.12 mA/cm2) decreases about 1.8 times when using SiO2. In TiO2/SiO2/Si samples (-5.70 mA/cm2) further decrease after post-oxidation annealing (POA) (−7.70 mA/cm2). As a result, it can be seen that by fabricating an ultra-thin high-density SiO2 layer, the lattice mismatch at the TiO2/Si interface is reduced and the photocurrent density is improved.

In this study, we conduct a numerical evaluation of the impact of the recovery time of a saturable absorber (SA) on the output performance of an Yb-doped fiber laser operating in the dissipative soliton regime. Particularly, we evaluate the output pulse characteristics, such as the pulse width, spectral bandwidth, pulse peak power, and pulse energy depending on the change in recovery time. Applying a too-slow SA recovery time above a certain critical value is shown to make the output pulse unstable and broken. Furthermore, we demonstrate that there is an optimum recovery time range for stable dissipative soliton pulse generation, depending on the cavity dispersion and modulation depth of the SA. Further, we perform an additional numerical simulation of the pulse compression to demonstrate the relationship between the output dechirped pulse width and SA recovery time. The optimum approach for the generation of the shortest dechirped pulses in the dissipative soliton regime will be to construct a fiber laser cavity with a small normal cavity group velocity dispersion and use an SA with an appropriate recovery time.

In this paper, we propose ExtraV, a framework for near-storage graph processing. It is based on the novel concept of graph virtualization , which efficiently utilizes a cache-coherent hardware accelerator at the storage side to achieve performance and flexibility at the same time. ExtraV consists of four main components: 1) host processor, 2) main memory, 3) AFU (Accelerator Function Unit) and 4) storage. The AFU, a hardware accelerator, sits between the host processor and storage. Using a coherent interface that allows main memory accesses, it performs graph traversal functions that are common to various algorithms while the program running on the host processor (called the host program) manages the overall execution along with more application-specific tasks. Graph virtualization is a high-level programming model of graph processing that allows designers to focus on algorithm-specific functions. Realized by the accelerator, graph virtualization gives the host programs an illusion that the graph data reside on the main memory in a layout that fits with the memory access behavior of host programs even though the graph data are actually stored in a multi-level, compressed form in storage. We prototyped ExtraV on a Power8 machine with a CAPI-enabled FPGA. Our experiments on a real system prototype offer significant speedup compared to state-of-the-art software only implementations.

We propose an approach called buffered compares , a less-invasive processing-in-memory solution that can be used with existing processor memory interfaces such as DDR3/4 with minimal changes. The approach is based on the observation that multibank architecture, a key feature of modern main memory DRAM devices, can be used to provide huge internal bandwidth without any major modification. We place a small buffer and a simple ALU per bank, define a set of new DRAM commands to fill the buffer and feed data to the ALU, and return the result for a set of commands (not for each command) to the host memory controller. By exploiting the under-utilized internal bandwidth using ‘compare-n-op’ operations, which are frequently used in various applications, we not only reduce the amount of energy-inefficient processor-memory communication, but also accelerate the computation of big data processing applications by utilizing parallelism of the buffered compare units in DRAM banks. We present two versions of buffered compare architecture-full-scale architecture and reduced architecture-in trade of performance and energy. The experimental results show that our solution significantly improves the performance and efficiency of the system on the tested workloads.

We evaluated the spatial-temporal dispersion of airborne nanomaterials during the use of spray consumer products and estimated the level of consumer inhalation exposure. A total of eight spray products including five propellant and three pump types were selected to evaluate the dispersion of airborne nanoparticles across time and space in a cleanroom which could control the background particles. Four products were advertised to contain silver and one contained titanium nanoparticles, while three products were specified no ENM but as being manufactured through the use of nanotechnology. We used direct-reading instruments with a thermodesorber unit to measure the particles (number, mass, surface area), as well as filter sampling to examine physicochemical characteristics. Sampling was conducted simultaneously at each location (1 m, near-field; 2, 3 m, far-field) by distance from the source. We estimated the inhaled doses at the breathing zone, and the doses deposited in each part of the respiratory tract using the experimental data and mathematical models. Nanoparticles released from the propellant sprays persisted in the air and dispersed over a large distance due to their small size (1466-5565 particles/cm

This paper proposes a modeling of expected link delay (i.e., data delivery delay) on a two-way road segment for carry-and-forward data delivery schemes in vehicular networks. Recently, a lot of vehicles can communicate with each other by dedicated short-range communications (DSRC) for vehicular networking. In the near future, more vehicles will be equipped with DSRC devices because of governmental policies for driving safety. In this paper, we derive a link delay model on a two-way road segment. This link delay model is essential to support multihop infrastructure-to-vehicle or vehicle-to-vehicle data delivery in vehicular networks as disruption tolerant networks. Through simulation, it is shown that our two-way link delay model is more accurate than the legacy two-way link delay model. Furthermore, by applying our model to data unicasting, we show that our model is precise enough to support the efficient data unicasting on vehicular networks.