Optimal Strategy Research Articles

Continuous bioethanol production from glucose-rich hydrolysate derived from wheat straw using a unique fed-batch cultivation method in a bioreactor

The present study provides solutions to the bioethanol industry’s main issues of the absence of production of maximum fermentable sugars from lignocellulosic biomass, the unsuitability of a single microorganism to convert the fermentable sugars (xylose and glucose) together to bioethanol, and the unavailability of fermentation technique to run the process unlimitedly with consistent yield and productivity. A novel fractional acid hydrolysis technology was demonstrated in this study, which produced more than 90% (w/w) of available glucose in wheat straw as glucose-rich hydrolysate (GRH). This hydrolysate was then made acid-free using a membrane-based acid separation unit to reuse the separated acid to make the hydrolysis process environmentally safe and chemically inexpensive. Thereafter, this acid-free GRH was fermented to bioethanol using a unique constant volume fed-batch fermentation technique under an optimum glucose-feeding strategy. Remarkably, this fermentation technique yielded optimal average bioethanol productivity (g/Lh), yield (g/g), and titer (g/L) of 7.147±0.533, 0.508±0.002, and 58.835±0.766; 5.722±0.529, 0.501±0.006, and 33.748±0.322, respectively, with more than 99% glucose utilization during ten fed-batch cycles of synthetic and GRH glucose. Notably, the high production of GRH from lignocellulosic biomass, acid separation and reuse, and continuous and consistent bioethanol production sets this study apart as a pioneering endeavor. Furthermore, the bioethanol profit of USD 0.019/kg biomass from the second batch onwards at a bioethanol selling price of USD 0.745/L suggests the feasibility of the current study for industrial-scale bioethanol production from lignocellulosic biomass.

Bio-organic substitution in tobacco (Nicotiana tabacum L) cultivation: Optimum strategy to lower carbon footprint and boost net ecosystem economic benefit

The partial substitution of organic manure for chemical nitrogen fertilizers, known as organic substitution, is widely regarded as a cleaner and more sustainable production strategy. However, few studies have quantified greenhouse gas emissions, product income and net ecosystem economic benefit (NEEB) using a life cycle assessment (LCA) approach, particularly for typical tobacco (Nicotiana tabacum L.) production. Here, we quantified the yield and quality of a typical tobacco production in Qujing, Yunnan, China, through field experiments and calculated its carbon footprint and NEEB using the LCA approach. Four organic substitution strategies were established with equal nitrogen inputs, including synthesized chemical fertilizer (SN), farmyard organic manure (NF), commercial organic manure (NC), and bio-organic (Trichoderma viride Pers.) manure (NT), each substituting 15% of synthesized nitrogen fertilizer. Compared to the SN strategy, the NT strategy significantly increased yield and income by 10.3% and 9.6%, respectively. In contrast, the NF strategy significantly reduced income, while the NC strategy showed no significant difference. Both the NC and NT strategies significantly reduced N2O cumulative emissions (by 15.9% and 8.0%, respectively), increased δSOC (by 38.4% and 15.0%, respectively), and decreased carbon footprint compared to the SN strategy. However, the NF strategy significantly increased the income-scaled carbon footprint, even though it also notably reduced N2O cumulative emissions (by 22.6%) and increased δSOC (by 7.9%). The NT strategy achieved a win-win scenario of low environmental risk and high economic returns of tobacco production with significantly increased NEEB (by 10.6%) compared to the SN strategy (37.60 × 103 CNY yr−1). This suggests that the bio-organic Trichoderma manure substituting 15% synthesized nitrogen fertilizer is the best organic substitution strategy for sustainable tobacco production.

Estimating Influenza Illnesses Averted by Year-Round and Seasonal Campaign Vaccination for Young Children, Kenya.

In Kenya, influenza virus circulates year-round, raising questions about optimum strategies for vaccination. Given national interest in introducing influenza vaccination for young children 6-23 months of age, we modeled total influenza-associated illnesses (inclusive of hospitalizations, outpatient illnesses, and non‒medically attended illnesses) averted by multiple potential vaccination strategies: year-round versus seasonal-campaign vaccination, and vaccination starting in April (Southern Hemisphere influenza vaccine availability) versus October (Northern Hemisphere availability). We modeled average vaccine effectiveness of 50% and annual vaccination coverage of 60%. In the introduction year, year-round vaccination averted 6,410 total illnesses when introduced in October and 7,202 illnesses when introduced in April, whereas seasonal-campaign vaccination averted 10,236 (October) to 11,612 (April) illnesses. In the year after introduction, both strategies averted comparable numbers of illnesses (10,831-10,868 for year-round, 10,175-11,282 for campaign). Campaign-style vaccination would likely have a greater effect during initial pediatric influenza vaccine introduction in Kenya; however, either strategy could achieve similar longer-term effects.

Prevalence and Parasitological Examination of Fish Parasites in Clarias gariefinus from Selected Fish Farms in Sokoto Metropolis, Nigeria

Study’s Excerpt The prevalence of fish parasites in fish farms within the Sokoto metropolis is assessed. The results revealed high prevalence of Camallanus spp. and Capillaria spp. among fish populations. Water quality analysis revealed that there is interaction between physicochemical parameters and parasite prevalence. A comprehensive approach to fish farm management and disease control is provided. Full Abstract Fish are known to be affected by parasites both internally and externally with detrimental effects on fish growth and development. This study aimed to determine the prevalence of fish parasites in selected fish farms in the Sokoto metropolis. A total of one hundred and twenty fish samples were collected from ten selected fish farms and subjected to microscopic examination. Water samples were collected from ten fish farms and analysed using the standard procedures recommended by the American Public Health Association. The results indicate that 35.0% of the fish were infected with the parasite (P<0.0300). Significant high prevalence of 50.0% and 48.1% was recorded in the gender and age groups of the fishes (P<0.0308) and (P=0.0003), respectively. However, a significantly high prevalence of 47.6%, 49.1% and 31.7% was also observed in the length, weight, and body part of the fishes (P<0.0.0000). This study identified two nematode species (Camallanus spp. and Capellaria spp.) with Camallanus spp. showing a higher prevalence of 60.3% was obtained in Camellanus spp. among the parasite species identified. The parameters such as pH, dissolved oxygen (DO) and nitrate (NO3) were assessed, and results were analysed using one-way analysis of variance (ANOVA) with the aid of SPSS version 27.0. The values of the physicochemical parameters were between the range of 6.68+0.11 to 7.83±0.05 for pH, 5.23+0.03 to 8.17±0.88 mg/L for DO, and 13.70+1.37 to 100.33+0.33 for NO3 respectively. All parameters examined were within acceptable limits recommended by the World Health Organization. Maintaining an optimum feeding strategy, regular monitoring of the water quality parameters and vaccinations will help to further decrease the rate of the parasite.

Penerapan Teori Permainan dalam Menentukan Strategi Pemasaran Optimum pada Produk Mi Instan (Mie Sedaap, Gaga, dan Supermi) di Lingkungan Mahasiswa Matematika Universitas Sumatera Utara

Instant noodle consumption in Indonesia has continued to increase in the last few years, which indicates that there are more business opportunities for instant noodle products in Indonesia. Proved by the number of instant noodle brands scattered on the market. This has led to increased competition among companies in order to be the best in the eyes of consumers. Marketing strategies are needed to win competition as well as increase sales, ranging from taste innovations, prices, product quality, promotions, and so on. In this study, game theory is used to investigate the competition between Mie Sedaap, Gaga, and Supermi. Using pure strategy is obtained game value that shows that the optimal strategy for Mie Sedaap is ease of purchase, the optimum strategy for Gaga is packaging strategy, and the optimum strategy for Supermi is price strategy.

Stock Prediction using Deep Learning: A Comparison

Stock market prediction (SMP) is one of the most important areas in finance that greatly helps investors and financial institutions to anticipate market fluctuations and make wise decisions. This becomes very important in view of the potential challenge of obtaining optimum revenues and effective portfolio management strategies in view of the volatile market environments typically governed by underlying economic and socio-political influences. This paper proceeds to categorize stock prediction works into three principal categories: Convolutional Neural Network (CNN)-based models, Recurrent Neural Network (RNN)-based models, and hybrid models using more than one forecasting technique. We reviewed nine research papers and compared them in view of different datasets to show efficacy distinctions among these methodologies. Our experiments stated that the hybrid models that marry the spatial data processing ability of CNNs to the temporal sensitivity of RNNs outperform other approaches in accuracy and strength of predictions. This synthesis approach captures complex patterns more efficiently as well as relevant to the dynamic nature of financial markets. Results underscore the potential contribution of hybrid frameworks being a leading methodology for future developments in SMP. Further improving these models with the advancements of machine learning and data analytics may likely push the boundaries of what is feasible in financial forecasting.

Hydrothermal liquefaction: exploring feedstock for sustainable biofuel production

A number of technological strategies utilizing various types of biomass for the production of hydrocarbons have been put forth but their energy intensive methods are a concern for improved efficiency of biofuel production. Hydrothermal liquefaction (HTL) has emerged as a promising and feasible technology towards utilization of lignocellulosic biomass. The suitability of different biomass feedstock for HTL is intricately tied to their macromolecular composition and process parameters. The comprehensive analysis of feedstock for hydrothermal liquefaction (HTL) signal towards the immense potential of various biomass feedstock, such as corn stover, Miscanthus, pine biomass, Spirulina, sugarcane bagasse, rice bran etc. in contributing significantly to renewable energy production. The study emphasizes that the composition of biomass is critical in influencing bio-oil yield during the HTL process. Biomass components like cellulose, hemicellulose, and lignin, each play distinct roles in determining the efficiency of conversion. Specifically, feedstock with higher cellulose and hemicellulose content, such as Miscanthus and sugarcane bagasse, demonstrate superior bio-oil yields. The analysis of proximate factors affecting HTL efficiency reveals that moisture content, ash content and high heating value (HHV) are pivotal in optimizing the process. In addition to composition and physical characteristics, the article underscores the significance of growth conditions and nutrient utilization in cultivating biomass feedstock. Integrating HTL with biomass cultivation can create a sustainable, closed-loop system where nutrients from the HTL process are recycled back into cultivation. Biomass offers a renewable energy alternative, however it also poses challenges related to land use and potential competition with food production. Sustainable practices, such as utilizing agricultural and forestry residues and optimizing collection as well as storage processes, can alleviate some of these concerns. By optimizing feedstock selection, process parameters, and integrating sustainable practices, HTL can play a decisive role in advancing biofuel production and contributing to a more sustainable energy future. The interplay between biomass composition, processing efficiency, environmental impacts, and economic feasibility is essential for realizing the full potential of HTL technology in the bio-economy. The current analysis sheds light on the relationship of bio-oil yield with macromolecular components including cellulose, hemicellulose, and lignin as well as process parameters like ash content, moisture content, higher heating value, fixed carbon and volatiles. Focusing on process optimization, this study embodies a closer analysis of literature aimed at defining optimum strategies for enhancement of HTL.

Development and psychometric assessment of the test “Predictive style”

BACKGROUND: Prognostic processes are an important link in adaptation to stressful events and resilience. The role of the features of prognostic abilities in various mental disorders is shown. We introduce and substantiate a new psychological construct, the “Predictive style”, reflecting the subjective importance of the forecasting process and the tendency to assess the favorability of predicted events. AIM: To develop and conduct a psychometric assessment of the “Predictive style” test. MATERIALS AND METHODS: A “Predictive style” test was developed, including 21 statements divided into 4 scales: excessive optimism, excessive pessimism, excessive forecasting and indifference to forecasts. The development of the test included the study of the external and internal validity, as well as the reliability of the methodology. RESULTS: The measures of compliance with the test model were at a sufficient level: CFI=0.927; TLI=0.917; SRMR=0.0538; RMSEA=0.0497 (95% CI 0.0403–0.0589) and were performed on a new sample. All items correlated with their scales at a sufficient level. The reliability of the scales was in an acceptable range: Kronbach α=0.851–0.630. Retest reliability was confirmed after 2 months. Convergent validity was demonstrated by correlations with levels of optimism, pessimism, anticipation, predictive ability and coping strategies. Statistically significant differences were found between the groups of patients with neurotic mental disorders and those without psychopathology. Multiple linear regression demonstrated that the test scales were statistically significant predictors of anxiety and depression symptoms in the study participants. The results obtained confirm the criteria validity of the test under development. CONCLUSION: The developed test has sufficient psychometric indicators and can be used in subsequent studies.

The surgical strategy selection and clinical efficacy analysis of Kummell's disease.

To evaluate the clinical efficacy of surgery in Kummell's disease (KD) to help us select the optimum surgical strategy. We included 67 KD patients who underwent Percutaneous vertebral plasty (PVP), Percutaneous kyphosis plasty (PKP), Percutaneous pedicle screw fixation (PPSF) or Posterior decompression osteotomy fixation (PDOF). The differences in imaging parameters and prognosis changes of pre-operation, post-operative and follow-up endpoint were analyzed. The incidence rate of KD was 10.02% (67/668) in vertebral compressibility fracture. 80.60% of patients underwent PVP/PKP, 14.93% underwent PPSF, and 4.47% underwent PDOF. The significant differences between the actual used surgical methods and the classification recommended surgical strategies could be found. In I type, there was no significant difference in total improvement of the radiography data and clinical efficacy between PVP and PKP. In II type, there was a significant correlation between opening and closing sign (OCS) and surgical choice. Compared with PPSF, the positive OCS patients who underwent PVP/PKP suffered a poor prognosis. PDOF is an effective surgical method for type III, but PVP could also achieve a good prognosis for patients with poor condition. The mainstream KD classification system has shortcomings, and completely following its treatment strategy may lead to poor prognosis. Compared to PKP, PVP is a better choice for type I patients. OCS is one of the important factors in surgical selection for type II patients. The Li's type III is mainly treated with PDOF but the overall condition of the body needs to be evaluated.

Fabrication and building energy-saving performance evaluation of polyethylene glycol/polymethyl methacrylate/expanded graphite thermal enhanced shape-stable phase change material

Integrating Phase Change Material (PCM) with building envelope is a promising way to reduce building energy consumption. However, leakage and insufficient PCM loading rate for existing encapsulation strategies limit its further application. In this work, a safer and easier way to fabricate Shape-Stable Phase Change Material (SSPCM) is proposed, whose products combine the outstanding leakage-proof property and high PCM loading rate. With the method of in-situ polymerization, not only the Polyethylene Glycol (PEG) is packaged by Polymethyl Methacrylate (PMMA), but the Expanded Graphite (EG) also has a chance to be added as the property regulator. The prepared SSPCMs are proved to be shape-stable over melting temperature with a leakage rate under 1 %. The characterization test reveals that with EG mass fraction increase from 0 to 2.5 %, the thermal conductivity augments from 0.23 to 1.73 W/(m·K) while the phase change latent enthalpy changes from 85.11 kJ/kg to 116.10 kJ/kg. Notably, the EG is more than a thermal conductivity enhancer, it also plays an important role in the modification of comprehensive properties. To optimize the building energy-saving performance of SSPCMs, the factors affecting building cooling electricity consumption like deployment position and thermal properties are evaluated in detail. The simulation results show that the optimum strategy is employing SSPCM with 2.0 wt% EG in the middle of the envelope, the cooling electricity consumption can be reduced by 8.64 % compared with the benchmark. The physical mechanism of energy-saving is also discussed from multiple angles. From a statistical view, sensitivity and uncertainty analysis of the simulation results is completed, to identify the influence of input parameters and validate the reliability of the simulation results. Finally, an economic analysis is carried out, proving the economic feasibility for further application. This research provides valuable insights for SSPCM’s application and design of energy-efficient buildings.

Occurrence of Ectoparasites on Tilapia zillii (Red Belly Tilapia) Gervais 1848 in The Tono Reservoir, Navrongo, Ghana

This study was carried out to assess the occurrence of endoparasites in (Tilapia zillii (Gervais, 1848)) from Tono reservoir, Navrongo Ghana. A total of 120 fish samples were collected from the upstream, midstream and downstream regions of the reservoir using cast nets. All the collected fish samples were transported to the research laboratory in the University for Development Studies and examined for ectoparasites during January 2022 to August 2022. Five ectoparasites namely Trichodina sp. of Protozoans ciliates, Dactyolgyrus sp. of Monogenean, Argulus sp. and Lernaea sp. of Crustaceans and the Diplostomum sp were identified. Overall prevalence of the fish parasites was 52.32 %. Intensity of the parasites observed ranged between 1.58% to 3.52%. Highest prevalence 70 % was reported in dry season while lowest (31.67%) was reported in the rainy season. Female fish samples had higher prevalence (64.47 %) than males (27.27 %). Fishes of downstream had highest prevalence (92.5 %) than upstream (17.5 %). Fish samples with maximum length and weight were highly (65.15 %) infected than small sized fish with low body length and weight (33.33 %). It is debatable if the degree of ectoparasite activity found in this study will constitute a serious danger to the local fish population. Yet, in order to stop disease outbreaks brought on by an increase in ectoparasites, the reservoir must be given significant attention by using optimum management strategies. This study shows that dry season affects the fish business and result in poor quality fish meat with risk of diseases infection.

Optimum management strategy for improving maize water productivity and partial factor productivity for nitrogen in China: A meta-analysis

China’s agricultural production suffers significant constraints due to low water productivity (WP) and partial factor productivity for nitrogen (PFPN). The pivotal solution to enhance maize yield, WP, and PFPN is through optimizing field management practices. However, previous studies primarily focused on the effects of individual or coupled field management practices on maize yield, WP, or PFPN in an area or land mass, so it is necessary to conduct a comprehensive quantitative analysis of various field management practices on maize yield, WP, and PFPN at the national scale. In this study, we compiled 286 studies encompassing 6959 pairs of experimental data spanning from 1990 to 2023. Meta-analysis was conducted to observe the variations in maize yield, WP, and PFPN across diverse field management practices (straw returning, nitrogen fertilizer application, irrigation practice, and tillage practice) on a national scale. The results showed that nitrogen fertilizer application (215 kg N ha−1) was the most effective in enhancing maize yield and WP by 68.1 % and 54.8 %, respectively. Additionally, irrigation had the most substantial impact on PFPN, enhancing 16.8 %. Straw mulching, application of slow and controlled release fertilizers, drip irrigation, and subsoiling were identified as the most effective practices in increasing maize yield, WP, and PFPN by Random forest model. Maize straw returning could reduce nitrogen fertilizer application by 20 kg ha−1, while increasing WP and PFPN by 4.2 % and 11.6 %, respectively. Moreover, straw returning could reduce water consumption by 23–60 mm, while increasing WP and PFPN by 2.9 % and 6.8 %, respectively. These findings can provide a reference for the formulation of comprehensive management strategies for sustainable maize production in China and globally.

A Low-Complexity Artificial Neural Network-Based Optimal Droop Gain Design Strategy for DC Microgrids Onboard the More Electric Aircraft

A Low-Complexity Artificial Neural Network-Based Optimal Droop Gain Design Strategy for DC Microgrids Onboard the More Electric Aircraft

CHOOSING AN OPTIMAL STRATEGY OF DEVELOPMENT OF THE INCLUSIFE TOURISM ECOSYSTEM: AN ECONOMIC AND MATHEMATICAL MODEL

The use of an ecosystem approach for the development of inclusive tourism can signif-icantly increase the availability of tourism services for people with special needs. At the same time, it is extremely important to choose an optimal strategy for the for-mation of this ecosystem, taking into ac-count a large number of options for the par-ticipation of potential stakeholders. The goal of the present paper is to develop an economic and mathematical model of the inclusive tourism ecosystem which can be used to substantiate the choice of the opti-mal strategy for its development.

Dynamic Event-Triggered Safe Control for Nonlinear Game Systems With Asymmetric Input Saturation.

This article focuses on the Pareto optimal issues of nonlinear game systems with asymmetric input saturation under dynamic event-triggered mechanism (DETM). First, the safe control is guaranteed by transforming the system with safety constraints into the one without state constraints utilizing barrier function. The united cost function integrating nonquadratic utility function is constructed to provide the foundation to achieve the Pareto optimal solutions. Then, the adaptive dynamic programming method with concurrent learning is proposed to approximate the Pareto optimal strategies wherein both current and historical data are utilized. To further lessen the consumptions of computation/communication resources, the DETM is integrated into the adaptive algorithm framework which can avoid Zeno phenomena. All the signals of the closed-loop system are proved to be uniformly ultimately bounded. Finally, the simulation results are given to validate the effectiveness of the proposed method from several aspects.

The efficacy and safety of dopamine versus norepinephrine in management of paediatric septic shock

Background: Septic shock is one of most common cause of death in pediatric patients. The optimum septic shock vasopressor support strategy is currently debated. This study was performed to evaluate the efficacy and safety of norepinephrine (NE) and dopamine (DA) as the initial vasopressor in pediatric septic shock patients. Methods: A prospective, randomized, clinical trial was carried out between January 2022 to January 2023 in a pediatric intensive care unit comparing DA with NE as the initial vasopressor in fluid-resuscitated 100 pediatric patients with septic shock. Normalization of blood pressure was taken as end point. If the maximum dose of the initial vasopressor was unable to attain the hemodynamic goal, then another vasopressor agent was added. Patients were monitored for response and side effect. Results: DA had a mortality of 50% as compared to 40% in NE. Arrhythmias occurred in 27.5% cases in DA group and 8.33% cases in NE group. There was a significantly greater incidence of sinus tachycardia with DA (12.5%) than NE (5%). Conclusions: NE showed better efficacy than DA in pediatric patients with septic shock with lesser event of arrhythmias.

Energy analysis during cold start and warm up period of a methanol engine hybrid power system under several novel energy conversion strategies

The use of methanol in engine hybrid power system has a wide range of potential applications, with the primary challenge being cold start issues. This paper innovatively proposes four strategies for starting and warming up the methanol engine, including motor dragging, motor dragging coupled with exhaust gas recirculation (EGR), motor dragging coupled with exhaust control, and motor dragging coupled with both EGR and exhaust control. These strategies can be implemented in methanol hybrid power system with minimal hardware modification costs, and not generate any emissions compared to traditional gasoline assisted strategy. The warm-up mechanisms of these strategies were analyzed and their effectiveness was verified by experiments. The optimum strategy, motor dragging coupling both EGR and exhaust control, has been demonstrated to enhance power input and improve the energy conversion efficiency substantially. Compared to the traditional gasoline assisted strategy, the energy consumption, energy conversion efficiency and the warm-up time in this strategy are 17.9 % lower, 5.1 % higher, 4.2 s shorter, respectively. These strategies well solve the problem of methanol engines being unable to start at low temperatures, which is expected to eliminate the cold start of the engine and directly enter the hot start.

Spontaneous mesenteric hematoma occurring during antithrombotic therapy and responsive to surgical treatment: a case report

BackgroundSpontaneous mesenteric hematoma is a rare condition that is diagnosed when clinical and pathological findings do not identify an obvious causative disease. Various treatment options for spontaneous mesenteric hematoma exist; however, there are no clear treatment criteria. Herein, we report a case of spontaneous mesenteric hematoma that was successfully treated surgically and discuss the optimum treatment strategy based on similar cases.Case presentationA 63-year-old man with abdominal persisting for 3 days presented to our hospital after going into shock without any triggers. The patient had a history of atrial fibrillation, stroke, and an aneurysm, and was receiving antithrombotic therapy. Abdominal contrast-enhanced computed tomography revealed a mass structure within the sigmoid mesentery, which was suspected to be a hematoma. The patient was admitted to the hospital for follow-up observation after initial infusion and vital stabilization. However, the following day, the patient developed acute generalized peritonitis with necrosis of the sigmoid colon; therefore, emergency Hartmann’s surgery was performed. Intraoperative and histopathological examinations revealed no evidence of bleeding.ConclusionSpontaneous mesenteric hematomas tend to be associated with intestinal necrosis and may require surgical treatment with bowel resection owing to the difficulty in identifying the responsible vessel. Moreover, our results suggest that the presence of antithrombotic therapy may be an important factor affecting spontaneous mesenteric hematoma development.

Aperiodically Intermittent Event-Triggered Optimal Average Consensus for Nonlinear Multi-Agent Systems.

This article is concerned with average consensus of multi-agent systems via intermittent event-triggered strategy. First, a novel intermittent event-triggered condition is designed and the corresponding piecewise differential inequality for the condition is established. Using the established inequality, several criteria on average consensus are obtained. Second, the optimality has been investigated based on average consensus. The optimal intermittent event-triggered strategy in the sense of Nash equilibrium and corresponding local Hamilton-Jacobi-Bellman equation are derived. Third, the adaptive dynamic programming algorithm for the optimal strategy and its neural network implementation with actor-critic architecture are also given. Finally, two numerical examples are presented to show the feasibility and effectiveness of our strategies.

Distributed Neurodynamics-Based Backstepping Optimal Control for Robust Constrained Consensus of Underactuated Underwater Vehicles Fleet.

Robust constrained formation tracking control of underactuated underwater vehicles (UUVs) fleet in 3-D space is a challenging but practical problem. To address this problem, this article develops a novel consensus-based optimal coordination protocol and a robust controller, which adopts a hierarchical architecture. On the top layer, the spherical coordinate transform is introduced to tackle the nonholonomic constraint, and then a distributed optimal motion coordination strategy is developed. As a result, the optimal formation tracking of UUVs fleet can be achieved, and the constraints are fulfilled. To realize the generated optimal commands better and, meanwhile, deal with the underactuation, at the lower-level control loop a neurodynamics-based robust backstepping controller is designed, and in particular, the issue of "explosion of terms" appearing in conventional backstepping-based controllers is avoided and control activities are improved. The stability of the overall UUVs formation system is established to ensure that all the states of the UUVs are uniformly ultimately bounded in the presence of unknown disturbances. Finally, extensive simulation comparisons are made to illustrate the superiority and effectiveness of the derived optimal formation tracking protocol.