Double Looping Research Articles

Futures empathy for foresight research and practice

Foresight methods help us to think about the future and overcome a bias toward short-term thinking in decision making. However, many approaches to investigating the future tend to leave implicit how individuals involved in the interventions relate to the present and to the future in practice and over time. To address this gap, our study highlights the affordances of two methodologies —Scenario Planning and Future Design. In a pilot study combining these methods, we report the results of the novel hybridized approach applied in strategic planning workshops across four corporations. Initial reflections and learnings from the pilot case study and literature review helps to build understandings of the practical and theoretical workings of the methodological innovation. By investigating this combination of foresight methodologies, this research opens up new ways for thinking about futuring and proposes a theory of Futures Empathy. Futures Empathy harnesses a person’s capacity for empathy in a novel way by applying it toward a future context. It consists of an iterative double looping process between self and a not yet existent future. Through imagination and reflection, foresight methods that build Futures Empathy can enhance personal connection and integration with a longer time horizon, thus overcoming presentism. By proposing a theory of Futures Empathy, we hope to contribute to better present and future relating in practice and over time across a multitude of foresight interventions.

Learning of Wheelchair Racing Propulsion Skills Over Three Weeks of Wheeling Practice on an Instrumented Ergometer in Able-Bodied Novices.

The acquisition of daily handrim wheelchair propulsion skill as a multi-layered phenomenon has been studied in the past. Wheelchair racing, however, is considerably different from daily handrim wheelchair propulsion in terms of propulsion technique, as well as the underlying equipment and interface. Understanding wheelchair racing skill acquisition is important from a general motor learning and skill acquisition perspective, but also from a performance and injury prevention perspective. The aim of the current lab-based study was 2-fold: to investigate the evolution of racing wheelchair propulsion skill among a sample of novices and to compare them with an experienced wheelchair racer under similar conditions. A convenience sample of 15 able-bodied novices (8 male, 7 female) completed a standardized three-week submaximal uninstructed practice protocol (3 weeks, 3 sessions per week, 3x4 min per session) in a racing wheelchair on an ergometer. Required wheeling velocity was set at 2.78 m/s (10 km/h) and a rolling friction coefficient of 0.011 (resulting in a mean target load of 21W) was used. For comparison, an experienced T54 Paralympic athlete completed one block of the same protocol. Kinetics, kinematics, and physiological data were captured. A mixed effects regression analysis was used to examine the effect of practice for the novices, while controlling for speed. All participants finished the protocol successfully. However, not all participants were able to achieve the target speed during the first few sessions. Statistically significant improvements over time were found for all outcome measures (i.e., lower metabolic strain, longer push and cycle times) with the exception of mean power and torque per push. The athlete used a significantly greater contact angle and showed “better” outcomes on most metabolic and kinetic variables. While the athlete used a semi-circular propulsion technique, most participants used a double looping over technique. Three weeks of uninstructed wheelchair racing practice significantly improved efficiency and skill among a group of novices, in line with previous studies on daily handrim wheelchair propulsion. The comparison with an experienced athlete expectedly showed that there is still a large performance (and knowledge) gap to be conquered.

Techno-economic assessment of a chemical looping splitting system for H2 and CO Co-generation

The natural gas (NG) reforming is currently one of the low-cost methods for hydrogen production. However, the mixture of H2 and CO2 in the produced gas inevitably includes CO2 and necessitates the costly CO2 separation. In this work, a novel double chemical looping involving both combustion (CLC) and sorption-enhanced reforming (SE-CLR) was proposed towards the co-production of H2 and CO (CLC-SECLRHC) in two separated streams. CLC provides reactant CO2 and energy to feed SECLRHC, which generates hydrogen in a higher purity, as well as the calcium cycle to generate CO in a higher purity. Techno-economic assessment of the proposed system was conducted to evaluate its efficiency and economic competitiveness. Studies revealed that the optimal molar ratios of oxygen carrier (OC)/NG and steam/NG for reforming were recommended to be 1.7 and 1.0, respectively. The heat integration within CLC and SECLRHC units can be achieved by circulating hot OCs. The desired temperatures of fuel reactor (FR) and reforming reactor (RR) should be 850 °C and 600 °C, respectively. The heat coupling between CLC and SECLRHC units can be realized via a jacket-type reactor, and the NG split ratio for reforming and combustion was 0.53:0.47. Under the optimal conditions, the H2 purity, the H2 yield and the CH4 conversion efficiency were 98.76%, 2.31 mol mol−1 and 97.96%, respectively. The carbon and hydrogen utilization efficiency respectively were 58.60% and 72.45% in terms of the total hydrogen in both steam and NG. The exergy efficiency of the overall process reached 70.28%. In terms of the conventional plant capacity (75 × 103 t y−1) and current raw materials price (2500 $ t−1), the payback period can be 6.2 years and the IRR would be 11.5, demonstrating an economically feasible and risk resistant capability.

A novel calcium looping–integrated NGCC power plant configuration for carbon capture and utilization—Comprehensive performance analysis

Energy plays a pivotal role in industrial development of any country. At present, most of the countries are utilizing fossil fuels, mainly coal and natural gas as energy sources for power production. However, these sources emit high amounts of carbon dioxide (CO2) into the atmosphere resulting in global warming. Hence, the fossil fuel–based thermal power plants need to be integrated with CO2 sequestration and utilization processes for sustainable power production. In this work, four natural gas combined cycle (NGCC) power plant configurations are proposed—two with CO2 capture and sequestration (single and double calcium looping units) and two with CO2 capture and utilization (for production of dimethyl ether). Energy, exergy, environmental, and economic analyses are carried out to assess the performance of the proposed novel configurations against the conventional NGCC power plant. These analyses reveal that the NGCC power plant integrated with double calcium looping unit captures 91.32% of CO2 with an energy penalty of 6.73%. The proposed CO2 capture and utilization integrated configurations have low electrical power output; however, the conversion of CO2 to high energy density dimethyl ether (DME) product resulted in overall energy and exergy efficiency gain. The CO2 capture and utilization configuration integrated with solar energy is able to convert the total captured CO2 to DME and makes the process sustainable.

Functional roles of antisense enhancer RNA for promoting prostate cancer progression.

Rationale: Enhancer RNA (eRNA) bi-directionally expresses from enhancer region and sense eRNA regulates adjacent mRNA in cis and in trans. However, it has remained unclear whether antisense eRNAs in different direction are functional or merely a reflection of enhancer activation.Methods: Strand-specific, ribosome-minus RNA sequencing (RNA-seq) were performed in AR positive prostate cancer cells. RNA-seq, GRO-seq, ChIP-seq, 4C-seq and DNA-methylation-seq that published in our and other labs were re-analyzed to define bi-directional enhancer RNA and DNA methylation regions. Molecular mechanisms were demonstrated by 3C, ChIP, ChIRP, CLIP, RT-PCR and western blot assays. The biological functions of antisense-eRNA were assessed using mice xenograft model and RT-PCR analysis in human tissues.Results: In this study, we identified that antisense eRNA was regulated by androgen receptor (AR) activity in prostate cancer cells. Antisense eRNA negatively regulated antisense ncRNA in AR-related target genes' loci, through recruiting DNMT1 on the antisense enhancer in the gene-ending regions and elevating DNA methylation. Importantly, the chromatin exhibited a double looping manner that facilitated sense-eRNA to promoter and antisense-eRNA to gene-ending region in cis. Depletion of antisense eRNA impaired its neighbor mRNA expression, cancer growth and invasion. The expressions of antisense eRNA were correlated with biochemical recurrence and clinical marker PSA's levels in patients' tissues.Conclusions: The findings indicated that antisense eRNA was a functional RNA and may be a novel target that when suppressed improved prostate cancer therapy and diagnosis. New chromatin interaction among enhancer, promoter and gene-ending region might provide new insight into the spatiotemporal mechanism of the gene transcription and acting of bi-directional eRNAs.

Energy and economic analysis of a hydrogen and ammonia co-generation system based on double chemical looping

In this work, a model of hydrogen production by double chemical looping is introduced. The efficiency benefit obtained was investigated. The chemical looping hydrogen generation unit is connected in series to the downstream of a chemical looping gasification unit as an additional system for 100 MW·h coal gasification, with the function of supplementary combustion to produce hydrogen. Using Aspen Plus software for process simulation, the production of H2 and N2 in the series system is higher than that in the independent Chemical looping gasification and Chemical looping hydrogen generation systems, and the production of hydrogen is approximately 25.63% and 12.90% higher, respectively; The study found that when the gasification temperature is 900 °C, steam-carbon ratio is 0.84 and oxygen-carbon ratio is 1.5, the hydrogen production rate of the system was the maximum. At the same time, through heat exchange between logistics, high-pressure steam at 8.010 × 104 kg·h−1 and medium-pressure steam at 1.101 × 104 kg·h−1 are generated, and utility consumption is reduced by 61.58%, with utility costs decreasing by 48.69%. An economic estimation study found that the production cost of ammonia is 108.66 USD·(t NH3)−1. Finally, cost of equipment is the main factors influencing ammonia production cost were proposed by sensitivity analysis.

Discussion

Dr Jonathan M. Chen (Philadelphia, Pa). The group at Royal Children's and Queensland Hospitals are truly to be commended on an enviable series of more than 1000 arterial switch operations with outstanding results, and certainly since the era of transesophageal echocardiography, congenital surgeons have come a long way in developing safe and reproducible techniques to overcome the challenges of complex coronary transfer. Single coronary, single ostium, double looping, intramural, all these variants had, for the most part, extraordinarily low mortality in this series across 30 years of study.

Retarding System of the Diafraged Rectangular Waveguide Type

In this paper, we propose fast and sufficiently accurate models for retarding systems (RS) such as double-shifted combs in a rectangular screen and RS of the looping waveguide type based on the diaphragm conductivity calculation in a rectangular waveguide (RW). The conductivity of the capacitive diaphragm in the RW is obtained for electric and magnetic wide walls. Multimode models based on functionals of electric and magnetic types are also proposed. The models facilitate correct account of losses. The dispersion of a double comb and looping waveguide with infinitely thin walls is calculated.

Thermodynamic Feasibility of Pure Hydrogen Production and Storage in Iron and Germanium Based Double Chemical Looping Process

Solid iron based low or medium temperature chemical loop is considered as a possible option of hydrogen storage and production. In the method, hydrogen is produced via iron oxidation with steam, and in the next phase iron oxide is reduced with hydrogen, synthesis gas or methane. In the reduction stage the reaction is terminated when the atmosphere still contains a large fraction of the reducing agent (often over 70 vol.%). In the paper the innovative idea of a double, iron and germanium based, chemical cycle was proposed. The thermodynamic calculations show that the reduction stage in the double iron-germanium cycle is more effective than the classical iron based loop.

Accelerating population balance-Monte Carlo simulation for coagulation dynamics from the Markov jump model, stochastic algorithm and GPU parallel computing

This paper proposes a comprehensive framework for accelerating population balance-Monte Carlo (PBMC) simulation of particle coagulation dynamics. By combining Markov jump model, weighted majorant kernel and GPU (graphics processing unit) parallel computing, a significant gain in computational efficiency is achieved. The Markov jump model constructs a coagulation-rule matrix of differentially-weighted simulation particles, so as to capture the time evolution of particle size distribution with low statistical noise over the full size range and as far as possible to reduce the number of time loopings. Here three coagulation rules are highlighted and it is found that constructing appropriate coagulation rule provides a route to attain the compromise between accuracy and cost of PBMC methods. Further, in order to avoid double looping over all simulation particles when considering the two-particle events (typically, particle coagulation), the weighted majorant kernel is introduced to estimate the maximum coagulation rates being used for acceptance–rejection processes by single-looping over all particles, and meanwhile the mean time-step of coagulation event is estimated by summing the coagulation kernels of rejected and accepted particle pairs. The computational load of these fast differentially-weighted PBMC simulations (based on the Markov jump model) is reduced greatly to be proportional to the number of simulation particles in a zero-dimensional system (single cell). Finally, for a spatially inhomogeneous multi-dimensional (multi-cell) simulation, the proposed fast PBMC is performed in each cell, and multiple cells are parallel processed by multi-cores on a GPU that can implement the massively threaded data-parallel tasks to obtain remarkable speedup ratio (comparing with CPU computation, the speedup ratio of GPU parallel computing is as high as 200 in a case of 100 cells with 10 000 simulation particles per cell). These accelerating approaches of PBMC are demonstrated in a physically realistic Brownian coagulation case. The computational accuracy is validated with benchmark solution of discrete-sectional method. The simulation results show that the comprehensive approach can attain very favorable improvement in cost without sacrificing computational accuracy.

Efficient GPU parallel computing of population balance—Monte Carlo method for coagulation

The population balance-Monte Carlo (PBMC) method has become increasingly popular because the discrete and stochastic nature of the MCmethod is especially suited for particle dynamics. However, for the two-particle events (typically, particle coagulation), the double looping over all simulation particles is required in normal PBMCmethods, and simulating particle coagulation is in general a challenging computational task due to its numerical complexity and the computing cost. The compute unified device architecture (CUDA) is a programming approach for performing scientific calculations on a graphics processing unit (GPU) as a data-parallel computing device. In this article we present an implementation of accelerating PBMCmethod based on the Inverse scheme and the Acceptance-rejection (AR) scheme for simulating particle coagulation on the GPU. The main idea is to implement the highly threaded data-parallel processing tasks by using GPU and serial computing of complex logic and transaction processing by CPU. Furthermore, the computation accuracy of the PBMC on GPU was validated with a benchmark, a CPU-based discrete-sectional method. To evaluate the accelerating performance, the computing time on the GPU against its sequential counterpart on the CPU was compared. The speedups show that the GPU can accelerate the PBMC by a factor from decades to more than one hundred, depending on the number of simulation particle.

Fast Monte Carlo simulation for particle coagulation in population balance

The Monte Carlo (MC) method for population balance modeling (PBM) has become increasingly popular because the discrete and stochastic nature of the MC method is especially suited for particle dynamics. However, for the two-particle events (typically, particle coagulation), the double looping over all simulation particles is required in normal MC methods, and the computational cost is O(Ns2), where Ns is the simulation particle number. This paper proposes a fast random simulation scheme based on the differentially-weighted Monte Carlo (DWMC) method. The majorant of coagulation kernel was introduced to estimate the maximum coagulation rate by a single looping over all particles rather than the double looping. The acceptance–rejection process then proceeded to select successful coagulation particle pairs randomly, and meanwhile the waiting time (time-step) for a coagulation event was estimated by summing the coagulation kernels of rejected and accepted particle pairs. In such a way, the double looping is avoided and computational efficiency is greatly improved as expected. Five coagulation cases for which analytical solutions or benchmark solutions exist were simulated by the fast and normal DWMC, respectively. It is found the CPU time required is orders of magnitude lower and only increases linearly with Ns; at the same time the computational accuracy is guaranteed very favorably.

Hydration-induced reactivation of spent sorbents for fluidized bed calcium looping (double looping)

The aim of this work was to study the hydration-induced reactivation of spent sorbents from a calcium looping process. The changes of the sorbent properties induced by hydration, the regeneration of the CO2 capture capacity and the attrition tendency of the material once reused in the looping cycle were investigated. To this end, a reference limestone was subjected to multiple calcination/carbonation cycles in a lab-scale fluidized bed reactor and then reactivated by water hydration at room temperature for different times. Results suggested that the sorbent under investigation should be hydrated for times as short as possible compatible with complete chemical hydration. In fact, long hydration times bring about cramming (chemical sintering) phenomena, lower enhancement in the active porosity, increased attrition tendency and reduced reactivation. Attrition/fragmentation data referring to as-received and reactivated sorbents were compared. Relationships among CO2 capture capacity, surface properties and attrition tendency were presented and critically discussed, taking into account also the results obtained for a different sorbent.

Manual Wheelchair Propulsion Patterns on Natural Surfaces During Start-Up Propulsion

Koontz AM, Roche BM, Collinger JL, Cooper RA, Boninger ML. Manual wheelchair propulsion patterns on natural surfaces during start-up propulsion. Objectives To classify propulsion patterns over surfaces encountered in the natural environment during start-up and compare selected biomechanical variables between pattern types. Design Case series. Setting National Veterans Wheelchair Games, Minneapolis, MN, 2005. Participants Manual wheelchair users (N=29). Intervention Subjects pushed their wheelchairs from a resting position over high-pile carpet, over linoleum, and up a ramp with a 5° incline while propulsion kinematics and kinetics were recorded with a motion capture system and an instrumented wheel. Main Outcome Measures Three raters classified the first 3 strokes as 1 of 4 types on each surface: arc, semicircular (SC), single looping over propulsion (SL), and double looping over propulsion (DL). The Fisher exact test was used to assess pattern changes between strokes and surface type. A multiple analysis of variance test was used to compare peak and average resultant force and moment about the hub, average wheel velocity, stroke frequency, contact angle, and distance traveled between stroke patterns. Results SL was the most common pattern used during start-up propulsion (44.9%), followed by arc (35.9%), DL (14.1%), and SC (5.1%). Subjects who dropped their hands below the rim during recovery achieved faster velocities and covered greater distances (.016≤ P≤.075) during start-up on linoleum and carpet and applied more force during start-up on the ramp compared with those who used an arc pattern ( P=.066). Conclusions Classifying propulsion patterns is a difficult task that should use multiple raters. In addition, propulsion patterns change during start-up, with an arc pattern most prevalent initially. The biomechanical findings in this study agree with current clinical guidelines that recommend training users to drop the hand below the pushrim during recovery.

Stroke Pattern and Handrim Biomechanics for Level and Uphill Wheelchair Propulsion at Self-Selected Speeds

Richter WM, Rodriguez R, Woods KR, Axelson PW. Stroke pattern and handrim biomechanics for level and uphill wheelchair propulsion at self-selected speeds. Objectives To investigate the natural stroke patterns of wheelchair users pushing on a level surface, to determine if users adapt their stroke patterns for pushing uphill, and to assess whether there are biomechanic advantages to one or more of the stroke patterns. Design Case series. Setting Biomechanics laboratory. Participants Twenty-six manual wheelchair users with a spinal cord injury. Intervention Subjects pushed their own wheelchairs at self-selected speeds on a research treadmill set to level, 3°, and 6° grades. Stroke patterns were measured using a motion capture system. Handrim biomechanics were measured using an instrumented wheel. Main Outcome Measures Stroke patterns were classified for both level and uphill propulsion according to 1 of 4 common classifications: arcing, semi-circular, single-looping (SLOP), and double-looping (DLOP). Biomechanic outcomes of speed, peak handrim force, cadence, and push angle were all compared across stroke classifications using an analysis of variance. Results Only 3 of the 4 stroke patterns were observed. None of the subjects used the semi-circular pattern. For level propulsion, the stroke patterns were fairly balanced between arcing (42%), SLOP (31%), and DLOP (27%). Subjects tended to change their stroke pattern for pushing uphill, with 73% of the subjects choosing the arcing pattern by the 6° grade. No statistically significant differences were found in handrim biomechanics or subject characteristics across stroke pattern groups. Conclusions Wheelchair users likely adapt their stroke pattern to accommodate their propulsion environment. Based on the large percentage of subjects who adopted the arcing pattern for pushing uphill, there may be benefits to the arcing pattern for pushing uphill. In light of this and other recent work, it is recommended that clinicians not instruct users to utilize a single stroke pattern in their everyday propulsion environments.

Safety glass/ear plug combination

The present invention consists of a device which removeably secures a standard set of earplugs to a pair of eyeglasses, preferably safety glasses, by double looping a standard cord with a pair of cord adjusters. A pair of double looped elastomeric temple securing means hold both a loop of the cord through one of each of their loops and an eyeglass temple piece through the other of their loops. The tips of the cord are provided with an annular binding surface which may be inserted into the end of a standard earplug cavity which is cylindrical in configuration and which secures the earplug to the cord tip by frictional engagement therewith.

Architecture of the myocardium in computed tomography.

To determine whether current concepts of myocardial organization were in fact the result of artifacts introduced by the dissection technique, a method comprising air injection of the coronary arteries (which gently separated the myocardial fibers) and computerized tomography was devised. Viewing the tomographs cinematographically confirmed the concept that the heart is formed by a double looping of myocardial fiber bands was correct. Examination of abnormal hearts, eg, one with Duchenne muscular dystrophy, shows that pathologic tissue disarrangements could also be identified.

The Double Suspension and Exponents of the Homotopy Groups of Spheres

A simply connected space X is said to have exponent pk at the prime p if pk annihilates the p-primary component of the homotopy groups w*(X). Relations between the double suspension Y2: S2-'--> Q2S2'+ and the p-th James-Hopf invariant Hp: QS2+' -> QS2Pn+' give that S2f+ has p2f as an exponent at any prime p. This was proved for p = 2 by I. M. James [8] and for p odd by H. Toda [15]. Let p be an odd prime. M. Barratt [unpublished] conjectured that pf is an exponent for S2f+' at p. No smaller power of p could be an exponent since B. Gray [6] has shown that w*(S2f+') contains infinitely many elements with order pf. These elements stabilize mod p to elements in the image of the stable J-homomorphism. By studying a map derived from the p-th James-Hopf invariant, P. Selick [13] has shown that Barratt's conjecture is true when n = 1. Suppose p is greater than 3. In our previous paper [4], we showed that there exists a map w: Q2S2n+l -> S2,n-1 of spaces localized at p which is of degree p on the bottom cell. We used this map to show that pn+l is an exponent for S2f+ ' at p. In the present paper, we refine these methods. We show that w can be chosen so that the composition ?2w with the double suspension is the double looping of the degree p map. This enables us to apply induction to Selick's result and thus prove Barratt's conjecture for all n. The map w: Q2S2n+1_> S21'-1 may have other implications in homotopy theory. Let D(n) be its homotopy theoretic fibre and let C(n) be the homotopy theoretic fibre of the double suspension ?2: S2f1-1 -___ Q2S2n+1. Homological calculations and certain fibrations support the conjecture that C(n) has the homotopy type of the loop space QD(pn). (As a by-product of a new proof of Selick's theorem, we show that C(1) has the homotopy type of QD(p).)

CHLOROPLAST MORPHOLOGY AND FINE STRUCTURE IN BRITISH FUCOIDS

SummaryChromatophores, principally from eggs, of representatives of the seven genera of the Fucales found in Britain were investigated with the electron microscope and the results are presented here.The chromatophores are bounded by two pairs of membranes inside which lamellations consisting of three or four non‐cohering thylakoids are embedded in a stroma. The stroma of some genera is extended into a simple projecting, stalked pyrenoid and the inner pair of membranes (chromatophore envelope) loop back on themselves to form a covering also to the pyrenoid. The outer pair of membranes (chromatophore E.R.) take no part. Alternatively, two pyrenoids in close proximity, enclosed by a double looping of the chromatopbore envelope, may be found; they lie one above the other either facing in opposite ways or at right angles to each other. More rarely, two widely separated pyrenoids may be found.Pyrenoids of this sort do not occur in association with the egg chromatophores in the Fucaceae (Fucus, Ascophyllum and Pelvetia), but they do occur in the eggs (but not in thallus cells) of members of the Cystoseiraceae (Bifurcaria and Cystoseira), with the exception of Halidrys, and in the Himanthaliaceae (Himanthalia). These pyrenoids are regarded as rudimentary, and as representing a stage close to total eclipse.Pyrenoids in such a natural group are suggested to have phyletic value, their presence being thought to be indicative of greater antiquity than their absence. Hence members of the Fucaceae are thought to be more specialized than members of the Cystoseiraceae. This statement is discussed in relation to earlier results (Manton, 1964, etc.) where the Cystoseiraceae were found to have other kinds of primitive features, and the Fucaceae other kinds of advanced features.