Monolithic, Optically Coupled, Multi-Section Mid-IR Quantum Cascade Lasers

Mid-infrared (mid-IR λ ≈ 3–12 μm), single-mode-emission Quantum Cascade Lasers (QCLs) are of significant interest for a wide range of applications, especially as the laser sources are chosen for laser absorption spectroscopy. In this work, we present the design, fabrication and characterization of multi-section, coupled-cavity, mid-IR quantum cascade lasers. The purpose of this work is to propose a design modification for a coupled-cavity device, yielding a single-mode emission with a longer range of continuous tuning during the pulse, in contrast to a 2-section device. This effect was obtained and demonstrated in the work. The proposed design of a 3-section coupled-cavity QCL allows for a single-mode emission with 35 dB side-mode suppression ratio. Additionally, the time-resolved spectra of the wavelength shift during pulse operation, show a continuous tuning of ~3 cm−1 during the 2 μs pulse. The devices were fabricated in a slightly modified, standard laser process using dry etching.

Smart SRUs Pre-Investment Utilizing Oxygen Enrichment Technology

This paper presents an unparalleled engineering assessment conducted to evaluate the feasibility of pre-investing in O2 enrichment technology, with the purpose of increasing the processing capacities of conventional air-based sulfur recovery units (SRUs). Ultimately, the goal is to minimize the overall number of required SRUs for a greenfield gas plant and, consequently, capture a significant cost-avoidance opportunity. The technology review revealed that a high-level O2 enrichment can double the processing capacity of air-based SRU, depending on the H2S content in acid gas. As H2S mole fraction in feed increases, the debottlenecking capability increases. For the project under assessment, the processing capacity of air-based SRUs showed a maximum increase of 80%. On the contrary, operating with high O2 levels, will elevate SRU reaction furnace temperature, and mandates installing high-intensity burners, along with special control and ESD functions, to manage potential risk and ensure safe operation. Additionally, the liquid handling section of SRUs (condensers, collection vessels, degassing vessels, sulfur storage tanks) should be enlarged to accommodate more sulfur production. Typically, the enriched oxygen can be supplied from air separation units (ASUs), which entails significant capital cost. Apart from these special design considerations, there are several advantages for adopting this technology. Oxygen enrichment removes significant nitrogen volumes, which reduces loads on Claus, tail gas treatment, and thermal oxidizer units. Hence, lower capital cost for new plants is acquired due to equipment size reduction. In addition, higher HP steam production and less fuel gas consumption are achieved. Conventionally, O2 enrichment technology is employed in the initial design stage or used to retrofit operating SRUs facilities. However, it is unique to consider O2 enrichment-design requirements as part of new air-based SRUs design for phased program development. The objective is to enable smooth transition to fully O2 enrichment operated SRUs at a later phase of the project without the need for any design modification. This exceptional pre-investment strategy has resulted into reducing the required number of SRUs at phase II from eight to five units; and accordingly, a significant cost avoidance was captured.

AN INTEGRATED SHIP RE-DESIGN/MODIFICATION STRATEGY

Herein, we present an integrated ship re-design/modification strategy that integrates the ‘Computer-Aided Design (CAD)’ and ‘Computational Fluid Dynamics (CFD)’ to modify the ship hull form for better performance in resistance. We assume a modular design and the ship hull form modification focuses on the forward module (e.g. bulbous bow) and aft module (e.g. stern bulb) only. The ship hull form CAD model is implemented with NAPA*TM and CFD model is implemented with Shipflow**TM. The basic ship hull form parameters are not changed and the modifications in some of the technical parameters because of re-designed bulbous bow and stern bulb are kept at very minimum. The bulbous bow is re-designed by extending an earlier method (Sharma and Sha (2005b)) and stern bulb parameters for re-design are computed from the experience gained from literature survey. The re-designed hull form is modeled in CAD and is integrated and analyzed with Shipflow**TM. The CAD and CFD integrated model is validated and verified with the ITTC approved recommendations and guidelines. The proposed numerical methodology is implemented on the ship hull form modification of a benchmark ship, i.e. KRISO container ship (KCS). The presented results show that the modified ship hull form of KCS - with only bow and stern modifications - using the present strategy, results into resistance and propulsive improvement.

Structural and Surfacial Modification of Carbon Nanofoam as an Interlayer for Electrochemically Stable Lithium-Sulfur Cells

Electrochemical lithium-sulfur batteries engage the attention of researchers due to their high-capacity sulfur cathodes, which meet the increasing energy-density needs of next-generation energy-storage systems. We present here the design, modification, and investigation of a carbon nanofoam as the interlayer in a lithium-sulfur cell to enable its high-loading sulfur cathode to attain high electrochemical utilization, efficiency, and stability. The carbon-nanofoam interlayer features a porous and tortuous carbon network that accelerates the charge transfer while decelerating the polysulfide diffusion. The improved cell demonstrates a high electrochemical utilization of over 80% and an enhanced stability of 200 cycles. With such a high-performance cell configuration, we investigate how the battery chemistry is affected by an additional polysulfide-trapping MoS2 layer and an additional electron-transferring graphene layer on the interlayer. Our results confirm that the cell-configuration modification brings major benefits to the development of a high-loading sulfur cathode for excellent electrochemical performances. We further demonstrate a high-loading cathode with the carbon-nanofoam interlayer, which attains a high sulfur loading of 8 mg cm−2, an excellent areal capacity of 8.7 mAh cm−2, and a superior energy density of 18.7 mWh cm−2 at a low electrolyte-to-sulfur ratio of 10 µL mg−1.

Review on the wearable health-care monitoring system with robust motion artifacts reduction techniques

Purpose Wearables are gaining prominence in the health-care industry and their use is growing. The elderly and other patients can use these wearables to monitor their vitals at home and have them sent to their doctors for feedback. Many studies are being conducted to improve wearable health-care monitoring systems to obtain clinically relevant diagnoses. The accuracy of this system is limited by several challenges, such as motion artifacts (MA), power line interference, false detection and acquiring vitals using dry electrodes. This paper aims to focus on wearable health-care monitoring systems in the literature and provides the effect of MA on the wearable system. Also presents the problems faced while tracking the vitals of users. Design/methodology/approach MA is a major concern and certainly needs to be suppressed. An analysis of the causes and effects of MA on wearable monitoring systems is conducted. Also, a study from the literature on motion artifact detection and reduction is carried out and presented here. The benefits of a machine learning algorithm in a wearable monitoring system are also presented. Finally, distinct applications of the wearable monitoring system have been explored. Findings According to the study reduction of MA and multiple sensor data fusion increases the accuracy of wearable monitoring systems. Originality/value This study also presents the outlines of design modification of dry/non-contact electrodes to minimize the MA. Also, discussed few approaches to design an efficient wearable health-care monitoring system.

Determination of Current Flow Induced by Transcutaneous Electrical Nerve Stimulation for the Treatment of Migraine: Potential for Optimization

Introduction: Transcutaneous electrical nerve stimulation (TENS) for migraine involves the application of pulsatile stimulation through electrodes placed on the forehead to target the underlying trigeminal nerves. It is a simple, safe modality and has secured clinical approval in several markets including the European Union and the United States. Despite nearing almost 7 years of use (postclinical approval), the exact mechanism of action is not fully known. Guided by the need to stimulate the trigeminal nerves bilaterally, electrode dimensions are simply required to extend enough to cover the underlying nerves. The goal of this study is to examine induced current flow [magnitude and spatial distribution of electric field (EF)] and another driver of stimulation [activating function (AF)] due to TENS therapy for migraine for the first time. We further consider the effect of changing the electrode dimension and shape and propose a design modification to deliver optimal flow.Methods: We developed the first ultra-high-resolution finite element (FE) model of TENS for migraine incorporating the target supratrochlear (ST) and the supraorbital (SO) nerves. We first simulated the clinically approved V-shaped geometry. We then considered three additional designs: extended V-shaped, idealized pill-shaped, and finally an extended V-shaped but with greater contact spacing (extended V-shaped +CS).Results: Our findings revealed that the clinically approved electrode design delivered substantially higher mean current flow to the ST nerve in comparison with the SO nerves (Medial: 53% and Lateral: 194%). Consideration of an extended design (~10 mm longer and ~ 4 mm shorter) and a pill-like design had negligible impact on the induced current flow pattern. The extended V-shaped +CS montage delivered relatively comparable current flow to each of the three target nerves. The EF induced in the ST nerve was 49 and 141% higher in the Medial and Lateral SO nerve, respectively. When considering maximum induced values, the delivery of comparable stimulation was further apparent. Given the existing electrode design's established efficacy, our results imply that preferential targeting of the ST nerve is related to the mechanism of action. Additionally, if comparable targeting of all three nerves continues to hold promise, the extended V-shaped +CS montage presents an optimized configuration to explore in clinical studies.

Improving the Response Performance of Anti-Surge Control Valve for Gas Compressors

Anti-surge control valves are used for the protection of gas compressors by opening to relief sudden pressures (surge) which could damage the compressor internals. It is of great importance that the response of the anti-surge valves to surge detection is swift and within a few seconds since a little delay could cause catastrophic damages to the compressor it is meant to protect. In this paper, a design modification was done on an existing anti-surge valve to improve its response time. The modified system was designed and implemented, installed, and commissioned on a mixed refrigerant compressor. The modified system was tested, and the response performance was recorded. Results obtained showed average percentage improvement of 86% to that of the initial system. Also, the response performance of the modified system was less than 3 seconds as compared to the initial set-up which averages 9 seconds. This is indeed a great improvement in comparison to the initial system.

A Review of Supercapacitors: Materials Design, Modification, and Applications

Supercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromising energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid supercapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spinning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various functionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclusions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.

Deterministic & Probabilistic Evaluations of Structures & Components Credited for Seismic Design Extension Conditions

There is "high confidence" in the ability of structures, systems and components (SSCs) of Nuclear Power Plants (NPPs) to perform as designed during Design Basis Accidents. For Design Extension Conditions (DECs), the SSCs are required to perform as designed with "reasonably high confidence." A deterministic design method is proposed to address DECs' higher demands in new and existing CANDU NPPs. The deterministic method builds on the current requirements of applicable codes and standards and recommends more relaxed acceptance criteria. Nevertheless, a means to probabilistically evaluate built-in margins exceeding demand induced by a DEC would provide a measure of the confidence in a DEC-assigned structure or component performing its function. Therefore, a probabilistic method that estimates the probability of survivability for a structure or component when subjected to the demand induced by a DEC is proposed. The probabilistic method could be used to indicate whether there is a need for applying design modification to existing design features to address demands of seismic DEC. The mean, 5-percentile, and 95-percentile fragility functions of these SSCs are used. These fragility functions are typically developed to determine the High-Confidence-Low-Probability-of-Failure value associated with the contribution of a structure or component to the overall plant seismic risk. Sample cases for design features that were implemented in existing CANDU NPPs to address DECs are presented. Both the deterministic and probabilistic methods are applied to cases of Civil structures, passive Mechanical & Electrical components as well as active Control & Instrumentation components.