Feasibility of Hydrogen Production by a Continuous Two-Stage (Dark/Dark) Fermentation System

2011 ◽  
Vol 374-377 ◽  
pp. 1000-1004
Author(s):  
Yuan Yuan Qu ◽  
Wan Qian Guo ◽  
Jie Ding ◽  
Nan Qi Ren
Keyword(s):  
Hydrogen Production ◽  
Organic Substrates ◽  
Hydrogen Production Rate ◽  
Two Stage ◽  
Fermentation System ◽  
Stirred Tank Reactors ◽  
Hydrogen Recovery ◽  
Second Stage ◽  
Anaerobic Acidification ◽  
Two Stages

Anaerobic hydrogen production in a continuous two-stage fermentation system was studied. Two continuously stirred tank reactors (CSTR) were employed to evaluate performances of the system. The first stage was fed with molasses wastewater, and the effluent discharged from the first stage was subsequently fed into the second stage. The hydrogen production rate (HPR) in the second stage achieved a remarkable increase from 1.76 L/d to 6.45 L/d during the operation by re-utilizing the residual substrates from the first reactor effluent. The two stages showed a similar metabolic pathway for biohydrogen fermentation. The hydrogen production yield (HY) and acidification efficiency increased markedly by more than 70% and 50% respectively, which indicated the hydrogen recovery and anaerobic acidification of organic substrates can be improved by the combined continuous two-stage hydrogen production process.

A novel two-stage method of plant seedlings classification based on deep learning

2021 ◽  
pp. 1-11
Author(s):  
Tianhong Dai ◽  
Shijie Cong ◽  
Jianping Huang ◽  
Yanwen Zhang ◽  
Xinwang Huang ◽  
...  
Keyword(s):  
Deep Learning ◽  
Learning Technology ◽  
Two Stage ◽  
Second Stage ◽  
Stage Classification ◽  
Different Types ◽  
Two Stages ◽  
Plant Seedlings

In agricultural production, weed removal is an important part of crop cultivation, but inevitably, other plants compete with crops for nutrients. Only by identifying and removing weeds can the quality of the harvest be guaranteed. Therefore, the distinction between weeds and crops is particularly important. Recently, deep learning technology has also been applied to the field of botany, and achieved good results. Convolutional neural networks are widely used in deep learning because of their excellent classification effects. The purpose of this article is to find a new method of plant seedling classification. This method includes two stages: image segmentation and image classification. The first stage is to use the improved U-Net to segment the dataset, and the second stage is to use six classification networks to classify the seedlings of the segmented dataset. The dataset used for the experiment contained 12 different types of plants, namely, 3 crops and 9 weeds. The model was evaluated by the multi-class statistical analysis of accuracy, recall, precision, and F1-score. The results show that the two-stage classification method combining the improved U-Net segmentation network and the classification network was more conducive to the classification of plant seedlings, and the classification accuracy reaches 97.7%.

Two stage regression model with constraints; admissible second stage parameter estimation

2013 ◽  
Vol 63 (3) ◽  
Author(s):  
Lubomír Kubáček
Keyword(s):  
Parameter Estimation ◽  
Regression Model ◽  
Two Stage ◽  
Second Stage ◽  
Regression Experiment ◽  
Two Stages

AbstractIf a regression experiment is realized in two stages, then two possibilities can occur in the second stage. Estimates of the first stage parameters either may be corrected by use of second stage measurements or they must stay unchanged. In the latter case, this requirement must be taken into account when estimating the second stage parameters. The situation is a little more complicated when constraints on both groups of parameters are imposed.

Multistage Sampling Designs in Fisheries Research: Applications in Small Streams

1984 ◽  
Vol 41 (11) ◽  
pp. 1575-1591 ◽  
Author(s):  
David G. Hankin
Keyword(s):  
Natural Habitat ◽  
Equal Length ◽  
Relative Cost ◽  
Two Stage ◽  
Second Stage ◽  
Small Streams ◽  
Multistage Sampling ◽  
Two Stages ◽  
Alternative Designs ◽  
Habitat Unit

A common, although generally unrecognized, use of multistage sampling designs in freshwater fisheries research is for estimation of the total number of fish in small streams. Here there are two stages of sampling. At the first stage one selects a sample of stream sections, usually of equal length, and at the second stage one estimates the total number of fish present in each selected section. This paper argues that the conventional practice of selecting stream sections of equal length is ill-advised on both biological and statistical grounds, and that errors of estimation of fish numbers within selected sections will usually be small compared with errors of estimation resulting from expansion of sampled sections to an entire stream. If stream sections are instead allowed to vary in size according to natural habitat units, then alternative two-stage sampling designs may take advantage of the probable strong correlation between habitat unit sizes and fish numbers. When stream sections of unequal sizes are selected with probabilities proportional to their size (PPS), or measures of the sizes of selected sections are incorporated into estimators, one may substantially increase precision of estimation of the total number of fish in small streams. Relative performances of four alternative two-stage designs are contrasted in terms of precision, relative cost, and overall cost-effectiveness. Choice among alternative designs depends primarily on the correlation between fish numbers and habitat unit sizes, on the total number of stream sections, and on sample size. Recommendations for choices among the designs are presented based on these criteria.

Results of first stage brachiobasilic and brachiobrachial fistula creation: Implications for staged versus single procedure decision making

2021 ◽  
pp. 112972982110052
Author(s):  
Mary Ottinger ◽  
Desiree Picone ◽  
Katrina Hseih ◽  
Mathew Wooster ◽  
Mark J London ◽  
...  
Keyword(s):  
Decision Making ◽  
Operating Room ◽  
Senior Author ◽  
Two Stage ◽  
Second Stage ◽  
Single Procedure ◽  
Av Fistulas ◽  
Two Stages ◽  
Lost To Follow Up

Introduction: Transposed brachiobasilic AV fistulas (BVT) have increasingly been performed in two stages. Published reports give conflicting results, perhaps in part as many reports of staged procedures eliminate those patients who “fail” the first stage (i.e. are lost to follow-up in addition to anatomic failure). Methods: A prospectively maintained database was reviewed to identify all patients at two institutions who underwent the first stage of planned two-stage BVT by the senior author. Success in this context was defined as patients who eventually underwent second stage fistula creation, leaving the operating room after the second stage with a patent, transposed fistula. Results: From October 2012 to June 2020, 218 patients underwent first-stage procedures. At the first visit, 185 (85%) of fistulas were patent, 23 (11%) were occluded, 8 (4%) of patients were lost to follow-up, and 2 (1%) died. In the interval before the second operation, another eight (4%) patients were lost to follow-up, two were cancelled for medical reasons, and two declined surgery, leaving a total of 173 patients who made it to the second stage (80%). At operation, four patients were found to have unusable veins, leaving a total of 169 patients who completed both stages. If all patients who underwent first stage are included, 77% of patients entering this pathway left the OR after their second stage with patent access. If those lost to follow-up are excluded, this number increases to 84%, while if all those lost to follow-up are assumed to mature, success increases to 85%. Conclusions: Depending on results in patients lost to follow-up, between 77% and 85% of patients undergoing first stage brachiobasilic fistulae undergo successful second stage transposition. These numbers are equivalent or slightly lower than published maturation rates for single-stage BVT, so there is little margin for failure at the second stage.

scholarly journals How contractual terms determine fiduciary duties: a two-stage process

2019 ◽  
Vol 70 (2) ◽  
pp. 242-262
Author(s):  
David Gibbs-Kneller ◽  
Derek Whayman
Keyword(s):  
Fiduciary Duty ◽  
Single Factor ◽  
Two Stage ◽  
Fiduciary Duties ◽  
Second Stage ◽  
Stage Process ◽  
Duty Of Loyalty ◽  
Two Stages

The determination of the scope of the fiduciary duty of loyalty, when created by contract, is not a unitary process. It is raised following a multi-factorial enquiry, which considers the nature of the engagement, in a first stage. Here, no single factor is conclusive. It is then, in a separate, second stage, reduced by qualifying contractual terms, which are applied almost strictly logically. This second stage uses the contractual doctrines of interpretation and implication. However, since it is a form of the fiduciary doctrine of authorisation, those contractual doctrines are modified according to fiduciary principles. We argue this follows from the underlying nature of the fiduciary obligation as a way of resolving its internal tensions. While this division has not yet been fully recognised in the cases, the courts have been inching towards it. However, not fully recognising this inevitable division and eliding the two stages has led to defective reasoning and outcomes.

scholarly journals Natural Mix Algae Possible Source of Renewable Energy, Environmental friendly Bio-hydrogen

2018 ◽  
Vol 27 (2) ◽  
pp. 31-38
Author(s):  
Muhammad Saleem Muhammad Muhammad Saleem Muhammad
Keyword(s):  
Renewable Energy ◽  
Carbon Source ◽  
Hydrogen Production ◽  
Hydrogen Gas ◽  
Algae Biomass ◽  
Clean Fuel ◽  
Second Stage ◽  
Environmental Friendly ◽  
Promising Area ◽  
Two Stages

Present study is an attempt to explore natural mix algae as a source of bio-hydrogen which is a renewable and environmental friendly clean fuel. Idea is to produce hydrogen in two stages; in first stage algae biomass is grown in light, oxygen and carbon source. In the second stage grown algae produce hydrogen in the absence of light, oxygen and sulfur. Results obtained during study showing that by using natural mix algae hydrogen up to 520 ml/l of algae biomass can be produce in one cycle. However, hydrogen gas can be produced in sufficient quantity up to three cycles. Biological hydrogen production with unicellular mix algae, found to be a promising area of research and conceptual by nature in the laboratory. This process needs to be explored more to prove the ability to use at commercial level. Still much work is required as to make process more economical and practical.

scholarly journals Changes in humidity and temperature inside the pine cones (Pinus sylvestris L.) in two stages seed extraction

2013 ◽  
Vol 74 (3) ◽  
pp. 205-214 ◽  
Author(s):  
Monika Aniszewska
Keyword(s):  
Pinus Sylvestris ◽  
Lower Limit ◽  
Extraction Process ◽  
Continuous Control ◽  
Air Humidity ◽  
Two Stage ◽  
Second Stage ◽  
Seed Extraction ◽  
Pine Cones ◽  
Two Stages

Abstract Temperature measurements were taken: (1) under opening scales, (2) at the seed, and (3) in the stem, of pine cones. Changes in temperature were only examined during the second stage of a two-stage seed extraction process. During this phase a permanent dehydration temperature of 50°C was used, following comparison over a ranges of temperatures, between a lower limit of 35°C and a higher limited of 50°C. The temperature was slowest to increase in the cone’s stem, and fastest to increase under opening scales. The temperature at the seed remained constant at around 43°C for the first hour of dehydration, before increasing to 50°C. The two-stages method of cone extraction employed here, with a permanent dehydration temperature of 50°C in second stage, can be used in extraction cabinets equipped with seed extractors that allow the continuous control of air humidity. The time spent soaking during the inter-stage break should last 5 minutes. Viability of seeds obtained in two-stages process was 78% to 89%

scholarly journals Two-Stage Collaborative Exams have Little Impact on Subsequent Exam Performance in Undergraduate Mathematics

2020 ◽  
Author(s):  
George Kinnear
Keyword(s):  
Positive Impact ◽  
Exam Performance ◽  
Control Group ◽  
Observational Methods ◽  
Undergraduate Mathematics ◽  
Two Stage ◽  
Subsequent Performance ◽  
Second Stage ◽  
Post Test ◽  
Two Stages

Abstract In this paper, I investigate whether two-stage exams aid learning in undergraduate mathematics, as measured by students’ performance on subsequent exams. In a two-stage exam, students complete the exam individually then form into groups to solve it again, with grades based on a combination of the two stages. Previous research in other disciplines has found mixed results about their effect on subsequent performance, and little is known about their use in undergraduate mathematics. Here, I report on three studies which investigate the use of two-stage exams in different undergraduate mathematics contexts. The first two studies replicate observational methods from previous research, and find indications of a positive impact from group collaboration. The third study is experimental and finds that, in a delayed post-test, there is no difference in performance between students who answered related questions in a two-stage exam format and a control group which had no collaborative second stage. The findings suggest that two-stage exams may have little impact on longer-term learning of mathematics, but instructors may still wish to use them to emphasise a collaborative classroom pedagogy.

scholarly journals PRODUKSI BIOHIDROGEN DARI HIDROLISAT AMPAS TAHU SECARA FERMENTASI ANAEROB MENGGUNAKAN KULTUR CAMPURAN

REAKTOR ◽  
2014 ◽  
Vol 15 (2) ◽  
pp. 87
Author(s):  
Amir Husin ◽  
Sarto Sarto ◽  
Siti Syamsiah ◽  
Imam Prasetyo
Keyword(s):  
Solid Waste ◽  
Reducing Sugar ◽  
Hydrogen Yield ◽  
Batch Experiments ◽  
Two Stage ◽  
Second Stage ◽  
One Stage ◽  
Initial Ph ◽  
Two Stages ◽  
By Products

Ampas tahu merupakan produk samping industri pengolahan tahu berbahan dasar kacang kedelai (Glysine max.).  Dalam studi ini, ampas tahu yang telah mengalami perlakuan-awal dengan metode yang berbeda dikonversi menjadi hidrogen menggunakan kultur campuran.  Pengaruh perlakuan-awal asam satu-tahap (0,5% dan 10% berat HCl) dan dua-tahap (tahap I 0,5%  dan tahap II 10% berat HCl) terhadap sakarifikasi ampas tahu juga diinvestigasi.  Lebih lanjut, pengaruh perlakuan awal asam satu-tahap maupun dua-tahap terhadap produksi hidrogen dan efisiensi degradasi gula tereduksi dibandingkan.  Yield total gula-tereduksi 503,73 mg/g ampas tahu diperoleh dari perlakuan-awal asam dua-tahap.  Nilai ini kurang lebih 4 kali lebih tinggi dibanding hasil dari perlakuan-awal asam satu-tahap menggunakan 0,5% berat HCl. Studi produksi biohidrogen dilakukan secara batch menggunakan kultur campuran dengan kondisi reaksi  35oC dan pH awal 6,5,  Hasil percobaan menunjukkan, bahwa yield hidrogen kumulatif  maksimum 0,928  mmol/g  ampas tahu diperoleh dari perlakuan  asam dua-tahap  atau meningkat 1,8 kali dibanding perlakuan satu-tahap menggunakan 0,5% berat HCl. Key words : ampas tahu,  perlakuan asam, produksi hidrogen Abstract Tofu solid waste is one of the by-products of tofu-processing industry.  In this study, batch experiments were carried out to convert tofu solid waste pretreated by different methods into hydrogen using mixed culture.  The effects of one-stage (0.5% or 10% HCl) and two-stage (first stage 0.5% HCl) and second stage 10% HCl) pretreatments on the saccharification of tofu solid waste were also studied.  Furthermore, the effects of  and/or  two- stages acid pretreatments on hydrogen production and degradation efficiencies the reducing-sugar (RS) were compared.  A maximum total RS yield of 503.73 mg/g-tofu solid waste was obtained from substrate pretreated with two-stages method.  It was approximately 4-fold greater than that from substrate pretreated with one-stage method using 0.5% wt HCl. At the reaction condition of 35oC, initial pH =  6.5, and RS concentration based on 2 grams of tofu solid waste pretreated, a maximum cumulative hydrogen yield was 0.928  mmol/g-tofu solid waste from substrate  pretreated  with  two-stages method.  It was approximately 1.8-fold greater than that from substrate pretreated with one-stage method using 0.5% wt HCl. The results show that two-stage acid preteatment can enhancing the amount of  reducing sugar in the mixture and hydrogen yield from tofu solid wastes. 

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