Pair Of Junctions Research Articles

Correlating framework structures and thermoelectric performance of metal–organic framework/carbon nanotube thermoelectric hybrids with n–p type inversion

Metal–organic frameworks (MOFs) show considerable promise as thermoelectric materials due to the inherently low thermal conductivities provided by their unique porous frameworks. Nevertheless, their applications are impeded by poor electrical conductivities and processabilities. Herein, novel n–p type carrier transport inversion MOF/carbon nanotube (CNT) thermoelectric hybrids are developed via controlled adjustment of the MOF/CNT composition. The low thermal conductivities of the MOFs provide optimized (zT) values of 0.071 and 0.025 for the n- and p-type thermoelectric hybrids, respectively. Moreover, a flexible thermoelectric generator consisting of seven p-n junction pairs in series provides a maximum open-circuit voltage of 11.2 mV and a maximum power of around 165.5 nW at a temperature difference of 20 K. This study introduces an alternative approach to creating high zT p- and n-type thermoelectric hybrids near room temperature by manipulating the composite ratio, and establishes a correlation between the framework structure and the thermoelectric performance, thereby supporting the development of MOF-based thermoelectric materials.

Synchronization of Bloch Oscillations in a Strongly Coupled Pair of Small Josephson Junctions: Evidence for a Shapiro-like Current Step.

Bloch oscillations are a fundamental phenomenon linking the adiabatic transport of Cooper pairs to time. Here, we investigate synchronization of the Bloch oscillations in a strongly coupled system of sub-100nm Al/AlO_{x}/Al Josephson junctions in a high-Ohmic environment composed of highly inductive meanders of granulated aluminum and high-Ohmic titanium microstrips. We observe a pronounced current mirror effect in the coupled junctions and demonstrate current plateaus, akin to the first dual Shapiro step in microwave experiments. These findings suggest that our circuit design holds promise for realizing protected Bloch oscillations and precise Shapiro steps of interest for current metrology.

Back-analysis of sprayed concrete lined (SCL) tunnel junctions at Liverpool Street Crossrail station

Sprayed concrete linings (SCL) offer a versatile method of tunnel construction, particularly in regard to forming junctions since the lining acts as a shell structure which can redistribute the stresses around the opening efficiently. This process is easy to understand conceptually but it is much more difficult to illustrate in calculations. Conventional calculation methods make a number of far-reaching simplifications such as the assumption of linear elastic behaviour in the lining. This often leads to overly conservative designs and a residual concern over the loads in the lining. This study compares detailed measurements of strains recorded by distributed fibre optic sensors at a pair of junctions on the Crossrail project in London with a sophisticated numerical model of these tunnels. Having demonstrated that the results of the numerical model are broadly consistent with this unique set of field data, a variety of influences on the model have been examined. This includes the excavation sequence, the constitutive model for the lining and adjacent structures. The results indicate significant scope for the improvement of SCL junction design. Future papers will present the more results from other parts of this study along with their implications for the design of tunnel junctions.

Hidden Symmetries in Acoustic Wave Systems.

Latent symmetries are hidden symmetries which become manifest by performing a reduction of a given discrete system into an effective lower-dimensional one. We show how latent symmetries can be leveraged for continuous wave setups in the form of acoustic networks. These are systematically designed to possess latent-symmetry induced pointwise amplitude parity between selected waveguide junctions for all low frequency eigenmodes. We develop a modular principle to interconnect latently symmetric networks to feature multiple latently symmetric junction pairs. By connecting such networks to a mirror symmetric subsystem, we design asymmetric setups featuring eigenmodes with domain-wise parity. Bridging the gap between discrete and continuous models, our work takes a pivotal step towards exploiting hidden geometrical symmetries in realistic wave setups.

Charge–Phase Duality and Cotunneling of Fluxons in SQUID-like Nanorings

Employing charge–flux duality for Josephson junctions and superconducting nanowires, we predict a novel effect of fluxon cotunneling in SQUID-like nanorings. This process is strictly dual to that of Cooper pair cotunneling in superconducting transistors formed by a pairs of Josephson tunnel junctions connected in series. Cooper pair cotunneling is known to lift Coulomb blockade in these structures at low temperatures. Likewise, fluxon cotunneling may eliminate the magnetic blockade of superconducting phase fluctuations in SQUID-like nanorings, driving them into an insulating state.

Design and Fabrication of a Thermopile-Based Thin Film Heat Flux Sensor, Using a Lead—Substrate Integration Method

An accurate and continuous measurement of heat flux is needed in many long-term operation facilities in order to monitor and improve the life of its machinery. A thin film heat flux sensor is usually fabricated via sputtering, according to different spatial arrangements of thermocouple junctions. A novel thin film heat flux sensor was designed, fabricated, and calibrated, but the connection between the thin film and the leads could not be fixed quickly and steadily. For this purpose, in this paper a method to seamlessly integrate the leads and the thin film has been proposed to improve the sensor output signal. The sensor is capable of simultaneously measuring surface heat flux and temperature magnitude, to address the current situation of the single design of heat flux sensors. The novel thin film heat flux sensor is structured as follows: Thirty pairs of NiCr-NiSi thermocouple junctions are deposited in an annular pattern on a well-designed ceramic substrate. Over the annular thermopile, a 2000 nm-thick thermal insulator layer is deposited to create a temperature gradient across the layers. In addition, in this study a new calibration method was used to evaluate the static and dynamic properties of this novel thin film heat flux sensor. The analysis and experimental results show that the heat flux calculated from the sensor output was in good agreement with the value obtained from the pre-calibrated standard sensor. The sensitivity and response time of the novel sensor were measured at 0.06 mV/(kW/m2) and 475 ms, respectively. The heat flux measurements made with the sensor presented good repeatability. The heat-transfer coefficient of the Al2O3 thin film was 4.477 w/(m∙k) for the novel thin film heat flux sensor described in this paper.

Quadruple node of triple junctions of grain boundaries in a Eu2+-doped solid solution of the ions K+, Rb+, Cl- and Br-: an epifluorescence microscopy study using the doping ion as a fluorochrome.

Epifluorescence microscopy was used to unveil the geometry and relative spatial orientation of an arrangement of crystal defects, consisting of a quadruple node of triple junctions of grain boundaries, in a Eu2+-doped solid solution of K+, Rb+, Cl- and Br-. The doping ion was utilized as a fluorochrome. Microscopy images of different optical cross-sections of the arrangement of crystal defects under study were recorded and used to build an electronic three-dimensional reconstruction of this arrangement. The geometry is that of an irregular tristetrahedron, centred at the quadruple node, so that the tristetrahedron legs, deviating from the lattice <111>-zone axis directions, lie along the triple junctions, whereas the tristetrahedron faces collapse onto the grain boundaries. The deviation angles as well as the angles defined by different triple junction pairs and different grain boundary pairs were measured. The orientational deviation is larger than that in a KI single crystal but lower than that in a solid solution of K+, Cl- and Br-, meaning that the structural equilibrium depends on the matrix lattice structural character. Uncompensated local nanostrains, due to the ion substitution, are associated with the observed decrement in structural stability, in relation to the KI case, whereas compensated local nanostrains, provoked by the simultaneous substitution of cations and anions, are argued to be responsible for the observed increment in structural stability, in relation with the K(Cl, Br) case. The optical characterization of the fluorochrome, the recording and processing of the microscopy images, the building of the electronic 3D reconstruction, the angular measure methodology and the geometrical modelling are all carefully described.

Low-cost seebeck power measurement system for characterization of thermoelectric junctions and modules

Development of thermoelectric materials and devices requires performance testing to assess improvements as compared against known control samples. Traditionally, this has been done by measuring the figure of merit. However, another important parameter for materials evaluation is the power output of a single P-N junction pair, typically performed by applying current to the circuit and measuring the Peltier temperature difference output. This approach often leads to errors due to contact resistive heating across interfaces within a device. An alternative approach is to evaluate a thermoelectric couple as a Seebeck generator that requires expensive meters ($20 k-$30 k) to measure milli-volt and milli-amp outputs. In order to enable materials evaluation without the need to use full device modules that are costly and time intensive to fabricate and test, this paper describes the development of low-cost (~$200) measurement circuit and shows data that validates the milli-volt and milli-amp outputs from a single thermoelectric couple.

Design, fabrication and characterization of a micro-fabricated stacked-wafer segmented ion trap with two X-junctions

We describe the implementation of a three-dimensional Paul ion trap fabricated from a stack of precision-machined silica glass wafers, which incorporates a pair of junctions for two-dimensional ion transport. The trap has 142 dedicated electrodes which can be used to define multiple potential wells in which strings of ions can be held. By supplying time-varying potentials, this also allows for transport and re-configuration of ion strings. We describe the design, simulation, fabrication and packaging of the trap, including explorations of different parameter regimes and possible optimizations and design choices. We give results of initial testing of the trap, including measurements of heating rates and junction transport.

Nanoburl Graphites.

A critical challenge for the application of graphite is low strength, which originates from the easy cleavage of graphite (0002) planes. Inspired by the burl strengthening mechanism observed in tree trunks, nanodiamond particles converted into graphite onions are used as "nanoburls" embedded in graphite (0002) lattice planes to eliminate the graphite (0002) plane cleavage of bulk graphites prepared by spark plasma sintering from graphite powders. Covalent bonds are built between carbon atoms by sp3 hybridization at the interface between the graphite onions and flakes, which triggers an electron redistribution to form positive/negative charge domains within. Thus, pairs of pseudo-Schottky junctions are created by the hybridization, which further enhances the bonding between the graphite onions and flakes. With these bonding mechanisms, and with voids between the graphite powders filled in by the volume expansion associated with the change of nanodiamonds to the graphite onions, the loose compaction of graphite powder becomes consolidated at 1700°C. The proposed nanoburl mechanism shows its potential and bestows the nanoburl graphites with strength five times that of conventional graphites prepared from graphite powders. The concept of nanoburl strengthening can be important in the microstructural design and property enhancement of other layered materials.

Vacant Parking Slot Recognition Method for Practical Autonomous Valet Parking System Using around View Image

The parking assist system (PAS) provides information of parking slots around the vehicle. As the demand for an autonomous system is increasing, intelligent PAS has been developed to park the vehicle without the driver’s intervention. To locate parking slots, most existing methods detect slot markings on the ground using an around-view monitoring (AVM) image. There are many types of parking slots of different shapes in the real world. Due to this fact, these methods either limit their target types or use predefined slot information of different types to cover the types. However, the approach using predefined slot information cannot handle more complex cases where the slot markings are connected to other line markings and the angle between slot marking is slightly different from the predefined settings. To overcome this problem, we propose a method to detect parking slots of various shapes without predefined type information. The proposed method is the first to introduce a free junction type feature to represent the structure of parking slot junction. Since the parking slot has a modular or repeated junction pattern at both sides, junction pair consisting of one parking slot can be detected using the free junction type feature. In this process, the geometrically symmetric characteristic of the junction pair is crucial to find each junction pair. The entrance of parking slot is reconstructed according to the structure of junction pair. Then, the vacancy of the parking slot is determined by a support vector machine. The Kalman tracker is applied for each detected parking slot to ensure stability of the detection in consecutive frames. We evaluate the performance of the proposed method by using manually collected datasets, captured in different parking environments. The experimental results show that the proposed method successfully detects various types of parking slots without predefined slot type information in different environments.

Efficiency improvement of graphene/silicon Schottky junction solar cell using diffraction gratings

This study investigated the performance of graphene/silicon Schottky junction solar cells and presented two structures based on graphene diffraction gratings to significantly enhance the efficiency of the cells. Rectangular and staircase graphene gratings were employed as the junction pairs for silicon. The main structure and the proposed structures were then investigated at different temperatures, silicon thicknesses, and doping levels. The results showed that graphene grating significantly increased the internal electric field and width of the depletion region compared to the main structure. Moreover, the graphene-silicon interface area was increased at the contact point, consequently decreasing the dangling bonds. These regions also act as anti-reflectors and reduce the reflection of sunlight. The efficiency of the proposed structures, thanks to the aforementioned features, has been reported to be three-fold greater than the main structure. For instance, at the temperature of 300 K, doping level of 1 × 1017 cm−3 and silicon thickness of 500 nm, the short-circuit current, open-circuit voltage, fill factor, and efficiency of the main structure were obtained as 20.3 mA/cm2, 0.154 V, 57.3%, and 1.8%, respectively. For the same conditions, these figures were obtained as 22.4 mA/cm2, 0.398 V, 73%, and 6.54% for the rectangular graphene grating, and 20.8 mA/cm2, 0.397 V, 73%, and 6.08% for the staircase graphene grating, respectively.

Splice-Junction-Based Mapping of Alternative Isoforms in the Human Proteome

SUMMARYThe protein-level translational status and function of many alternative splicing events remain poorly understood. We use an RNA sequencing (RNA-seq)-guided proteomics method to identify protein alternative splicing isoforms in the human proteome by constructing tissue-specific protein databases that prioritize transcript splice junction pairs with high translational potential. Using the custom databases to reanalyze ~80 million mass spectra in public proteomics datasets, we identify more than 1,500 noncanonical protein isoforms across 12 human tissues, including ~400 sequences undocumented on TrEMBL and RefSeq databases. We apply the method to original quantitative mass spectrometry experiments and observe widespread isoform regulation during human induced pluripotent stem cell cardiomyocyte differentiation. On a proteome scale, alternative isoform regions overlap frequently with disordered sequences and post-translational modification sites, suggesting that alternative splicing may regulate protein function through modulating intrinsically disordered regions. The described approach may help elucidate functional consequences of alternative splicing and expand the scope of proteomics investigations in various systems.

Problems and methods of improving the quality of jaw crushers

Practically in all metallurgical treatment the raw product needs to be crushed by crushing machines. The main indicator of the crushers quality, which characterize their technical level and competitiveness, is their reliability and durability in the operating conditions, which can be quantitatively assessed by the number of failures in the process of obtaining the finished product on the machine. Among numerous technical reasons for the relatively short, but rather frequent downtimes in the operating conditions of jaw crushers, a significant place is occupied by the downtimes associated with the replacement of the plain bearing liners due to their wear. The rapid wear of liners is the result of not only contact friction between the axle trunnions and liners, but also the action of dynamic forces. The dynamic forces arising from the operation of jaw crushers are due to the presence of a gap in the kinematic pair of link junctions and velocities discrete values of the relative displacement of the links inside the gaps of the friction bearing. Consequently, the reliable operation of the machine largely depends on the creation of conditions that ensure the backlash-free contact of the mating links. It was experimentally proven that the use of mechanisms for taking up the wear of bearings with elastic elements that during the entire cycle of operation of the crank-beam mechanism taking up the wear in the kinematic pairs mating, prevents the appearance of additional dynamic loads and, thereby, increases the reliability of jaw crushers. Thus, the quality of the machine increases, as well as its productivity.

V-groove etched 1-eV-GaInNAs nipi solar cell

Simulated and experimental properties of a Ga1−xInxAs1−yNy nipi solar cell involving V-grooves for contact formation are reported. In particular, using a drift–diffusion model, we simulate the conversion efficiency, the short-circuit current density (JSC), and the open-circuit voltage (VOC) as a function of the number of nipi junctions. Based on the modelling results, optimized nipi solar cell incorporating five n–p junction pairs was grown on a p-type GaAs (100) substrate using molecular beam epitaxy (MBE). The bandgap of the nipi structure was determined to be 1 eV. The metal contacts of the nipi solar cell structure were processed in the form of mesa and V-groove. These shapes enable both vertical and horizontal carrier transport within the solar cell. The effect of thermal annealing on J–V characteristics of both type of devices is finally assessed. The results point out that the V-groove sample has better photovoltaic characteristics than the mesa structure sample.

Comprehensive Profiling of Four Base Overhang Ligation Fidelity by T4 DNA Ligase and Application to DNA Assembly.

Synthetic biology relies on the manufacture of large and complex DNA constructs from libraries of genetic parts. Golden Gate and other Type IIS restriction enzyme-dependent DNA assembly methods enable rapid construction of genes and operons through one-pot, multifragment assembly, with the ordering of parts determined by the ligation of Watson-Crick base-paired overhangs. However, ligation of mismatched overhangs leads to erroneous assembly, and low-efficiency Watson Crick pairings can lead to truncated assemblies. Using sets of empirically vetted, high-accuracy junction pairs avoids this issue but limits the number of parts that can be joined in a single reaction. Here, we report the use of comprehensive end-joining ligation fidelity and bias data to predict high accuracy junction sets for Golden Gate assembly. The ligation profile accurately predicted junction fidelity in ten-fragment Golden Gate assembly reactions and enabled accurate and efficient assembly of a lac cassette from up to 24-fragments in a single reaction.

Flexible and Transparent Organic-Inorganic Hybrid Thermoelectric Modules.

Light-weight, mechanically flexible, transparent thermoelectric modules are promising as portable and easy-to-integrate energy sources. Here, we demonstrate flexible, transparent thermoelectric modules by using a conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the p-type leg and indium tin oxide (ITO)-PEDOT:PSS as the n-type leg. Main observations include the following: (1) the bilayer combination of ITO-PEDOT:PSS (PEDOT:PSS coated on top of the ITO) displays a negative Seebeck coefficient ( S) and the value is similar to that of the ITO single layer; (2) the S value of the ITO-PEDOT:PSS is almost not dependent on the area ratio of the stacked PEDOT:PSS and ITO; and (3) the conducting polymer PEDOT:PSS deposition on top of ITO helps the ITO not to generate cracks during bending, which enhances the mechanical flexibility of the ITO. On the basis of these observations, thermoelectric modules with eight pairs of junctions are fabricated and the thermoelectric modules' Δ V/Δ T (modules' generated thermovoltage per temperature difference) is nearly the addition of S values of all legs. Thermoelectric modules show good mechanical flexibility and air stability. Applications of thermoelectric modules have also been demonstrated to produce thermovoltage via the temperature difference produced by a human hand or warm water.

Normal metal - insulator - superconductor thermometers and coolers with titanium-gold bilayer as the normal metal

We have fabricated superconductor - insulator - normal metal - insulator - superconductor (SINIS) tunnel junctions in which Al acts as the superconductor, AlOx is the insulator, and the normal metal consists of a thin Ti layer (5 nm) covered with a thicker Au layer (40 nm). We have characterized the junctions by measuring their current-voltage curves between 60 mK and 750 mK. For comparison, the same measurements have been performed for a SINIS junction pair whose normal metal is Cu. The Ti-Au bilayer decreases the SINIS tunneling resistance by an order of magnitude compared to junctions where Cu is used as normal metal, made with the same oxidation parameters. The Ti-Au devices are much more robust against chemical attacks, and their lower tunneling resistance makes them more robust against static charge. More significantly, they exhibit significantly stronger electron cooling than Cu devices with identical fabrication steps, when biased close to the energy gap of the superconducting Al. By using a self-consistent thermal model, we can fit the current-voltage characteristics well, and show an electron cooling from 200 mK to 110 mK, with a non-optimized device.

Faucet: streaming de novo assembly graph construction.

MotivationWe present Faucet, a two-pass streaming algorithm for assembly graph construction. Faucet builds an assembly graph incrementally as each read is processed. Thus, reads need not be stored locally, as they can be processed while downloading data and then discarded. We demonstrate this functionality by performing streaming graph assembly of publicly available data, and observe that the ratio of disk use to raw data size decreases as coverage is increased.ResultsFaucet pairs the de Bruijn graph obtained from the reads with additional meta-data derived from them. We show these metadata—coverage counts collected at junction k-mers and connections bridging between junction pairs—contain most salient information needed for assembly, and demonstrate they enable cleaning of metagenome assembly graphs, greatly improving contiguity while maintaining accuracy. We compared Fauceted resource use and assembly quality to state of the art metagenome assemblers, as well as leading resource-efficient genome assemblers. Faucet used orders of magnitude less time and disk space than the specialized metagenome assemblers MetaSPAdes and Megahit, while also improving on their memory use; this broadly matched performance of other assemblers optimizing resource efficiency—namely, Minia and LightAssembler. However, on metagenomes tested, Faucet,o outputs had 14–110% higher mean NGA50 lengths compared with Minia, and 2- to 11-fold higher mean NGA50 lengths compared with LightAssembler, the only other streaming assembler available.Availability and implementationFaucet is available at https://github.com/Shamir-Lab/Faucet Supplementary information Supplementary data are available at Bioinformatics online.

RSFQ/ERSFQ Cell Library With Improved Circuit Optimization, Timing Verification, and Test Characterization

We address all round development of the standard cell library including simulation, layout, and testing. We present a new circuit analysis scheme based on Monte-Carlo simulations and process corners. Using a phase modulation decoder as an example circuit, we identify weak spots in the design that was originally optimized for parameter margins. To support static timing analysis for very high complexity circuits, we describe the timing characterization of library cells as a function of its load, and demonstrate digital timing verification with timing back-annotation using Verilog hardware descriptive language. For the layout of library cells, we present architecture for the dual RSFQ/ERSFQ standard cell library for the MIT-LL, 10 kA/cm2, SFQ4EE and SFQ5EE processes. Testing and characterizing hundreds of library cells, including unique cells and their layout variations, is a challenge. For efficient characterization of the digital cells, we have developed an NDRO cell-based multiplexing scheme that lets us characterize hundreds of cells on a single chip. For better model-to-hardware correlation, we have implemented a differential delay measurement scheme using ring oscillators that facilitates timing characterization of the synchronous and asynchronous cells. We also report design and measurement of statistical variations for the critical current of decision-making pair of junctions.