Control of M/Cox-2/s make-to-stock systems

This study considers a make-to-stock production system with multiple identical parallel servers, fixed production start-up costs and lost sales. Processing times are assumed to be two-phase Coxian random variables that allows us to model the systems having rework or remanufacturing operations. First, the dynamic programming formulation is developed and the structure of the optimal production policy is characterized. Due to the highly dynamic nature of the optimal policy, as a second contribution we propose an easy-to-apply production policy. The proposed policy makes use of the dynamic state information and controlled by only two parameters. We test the performance of the proposed policy at several instances and reveal that it is near optimal. We also assess the value of dynamic state information in general by comparing the proposed policy with the well-known static inventory position based policy.

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Cooperative Control for Damping Inter-Area Oscillations Using Dynamic State Information

IEEE Access ◽

10.1109/access.2019.2922732 ◽

2019 ◽

Vol 7 ◽

pp. 77877-77884

Author(s):

Yan Xu ◽

Fushuan Wen ◽

Chung-Li Tseng ◽

Zeng Yang ◽

Minghui Chen ◽

...

Keyword(s):

Cooperative Control ◽

Dynamic State ◽

State Information

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Productivity Influence Factors of Tight Sandstone Gas Reservoir with Water Produced

Geofluids ◽

10.1155/2021/9926299 ◽

2021 ◽

Vol 2021 ◽

pp. 1-9

Author(s):

Yongchao Xue ◽

Qingshuang Jin ◽

Hua Tian

Keyword(s):

Pressure Gradient ◽

Relative Permeability ◽

Gas Flow ◽

Influence Factors ◽

Stress Sensitivity ◽

Consumption Pattern ◽

Tight Sandstone ◽

Gas Reservoir ◽

Two Phase ◽

Start Up

Finding ways to accelerate the effective development of tight sandstone gas reservoirs holds great strategic importance in regard to the improvement of consumption pattern of world energy. The pores and throats of the tight sandstone gas reservoir are small with abundant interstitial materials. Moreover, the mechanism of gas flow is highly complex. This paper is based on the research of a typical tight sandstone gas reservoir in Changqing Oilfield. A strong stress sensitivity in tight sandstone gas reservoir is indicated by the results, and it would be strengthened with the water production; at the same time, a rise to start-up pressure gradient would be given by the water producing process. With the increase in driving pressure gradient, the relative permeability of water also increases gradually, while that of gas decreases instead. Following these results, a model of gas-water two-phase flow has been built, keeping stress sensitivity, start-up pressure gradient, and the change of relative permeability in consideration. It is illustrated by the results of calculations that there is a reduction in the duration of plateau production period and the gas recovery factor during this period if the stress sensitivity and start-up pressure gradient are considered. In contrast to the start-up pressure gradient, stress sensitivity holds a greater influence on gas well productivity.

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Value Addition to Beans: The Case of Bean Balls “Akara” Production in Idemili South Local Government of Anambra State, Nigeria

Asian Journal of Agricultural Extension Economics & Sociology ◽

10.9734/ajaees/2019/v33i230173 ◽

2019 ◽

pp. 1-7

Author(s):

T. N. Nwankwo ◽

T. O. Okoli ◽

C. O. A. Ugwumba

Keyword(s):

Local Government ◽

Raw Materials ◽

Net Income ◽

Market Prices ◽

Anambra State ◽

Electricity Use ◽

Multi Stage ◽

Production Policy ◽

Start Up ◽

Policy Measures

Aims: The study examined socio-economic characteristics of the bean balls producers, the profitability of production, determinants of profit, reasons for starting the business and constraints to production of bean balls in Idemili South Local Government Area of Anambra State, Nigeria. The great need to help homemakers in Nigeria better appreciate and prepare cowpea bean balls as snacks for income generation and women empowerment in Nigeria informed this study. Study Design: Multi-stage, purposive and random sampling techniques were used to select 50 respondents. Data were collected using structured questionnaire and analyzed by means of descriptive and inferential statistics. Results: Findings on socio-economic factors of the respondents gave mean age, education level and years of experience of 42.4years, 13.5years and 8.9 years respectively; the majority (92%) of the respondents were females, the majority (60%) married and most (70%) had a household size of 4-6 persons. The enterprise proved profitable with monthly mean net income and net return on investment values of ₦75,990 and 0.39 respectively. Significant determinants of net production returns were gender, educational level and costs of inputs. Main reasons for starting the business were a scarcity of job, profitable nature of the business, high demand and small start-up capital. Serious constraints to production of bean balls in the area were conjunctivitis due to emitted smoke, high and unstable price of raw materials and high cost of production. Policy measures such as bulk purchasing of beans, regulation of market prices of the product, provision of infrastructures (water, electricity), use of cooking gas as a source of heat would mitigate the problems, improve productivity, output and enterprise profitability. Conclusion: The bean ball production proved to be a profitable enterprise in the study area. Nevertheless, the efficiency and profitability would be improved if the constraints identified by the study are addressed as it will encourage many more people especially young, active and viable individuals, to venture into the enterprise.

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Research on the Start-Up Effect of Two-Phase Anaerobic Baffled Reactor

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.448-453.600 ◽

2013 ◽

Vol 448-453 ◽

pp. 600-603

Author(s):

Ling Jing ◽

Xin Xia Wang

Keyword(s):

Wastewater Treatment ◽

Ph Value ◽

Removal Rate ◽

Limiting Factors ◽

Small Cities ◽

Two Phase ◽

Anaerobic Reactor ◽

Anaerobic Baffled Reactor ◽

Low Concentration ◽

Start Up

Aiming at the fact that the low concentration sewage in small cities, this paper presents Two-phase Anaerobic Baffled Reactor (TAABR) for living wastewater treatment, importantly, it designs and researches Two-phase Anaerobic Baffled Reactor and its advantages, designs a trial project according to the characteristics of the reactor equip. The experiment uses the method that by shortening HRT to raise the load to start and analyses the operating results during startup as follows: 1. 53 days later anaerobic reactor start-up successes.2. When the load is 0.5kgCOD/m3.d, the removal rate of COD is more than 80%. 3. PH value is not the main limiting factors during start up in the reactor and there is basically no danger of excessive acidification.

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Analysis of ABWR Critical Control Operation by TRACG Code

Volume 5: Fuel Cycle and High and Low Level Waste Management and Decommissioning; Computational Fluid Dynamics (CFD), Neutronics Methods and Coupled Codes; Instrumentation and Control ◽

10.1115/icone17-75143 ◽

2009 ◽

Author(s):

Yoshihiko Ishii ◽

Kazuaki Kitou ◽

Tomohiko Ikegawa ◽

Shin Hasegawa ◽

Hitoshi Ochi

Keyword(s):

Diffusion Theory ◽

Three Dimensional ◽

Source Model ◽

Control Mode ◽

Two Phase ◽

Control Rod ◽

Start Up ◽

Neutron Count ◽

Calculation Results ◽

Operation Timing

Hitachi utilized three-dimensional transient analysis to design and verify a critical-control mode algorithm of an automatic power regulator (APR). TRACG has a three-dimensional neutron kinetics model based on diffusion theory and a six-equation two-phase flow model. To verify the APR critical-control mode algorithm, an external-neutron-source model that makes possible to simulate a sub-critical initial core, and an APR system model were developed and added on TRACG. The code was verified by comparison of measurements and calculation results of ABWR start-up operation under the critical-control mode. The modified TRACG could simulate neutron count rates of start-up-range neutron monitors (SRNMs), reactor period, control rod operation timing, CR withdrawal length, and time of criticality declaration, well.

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Start up of Thermophilic UASB (Upflow Anaerobic Sludge Blanket) Reactors Using Micro-Carrier and Mesophilic Granular Sludge

Water Science & Technology ◽

10.2166/wst.1992.0468 ◽

1992 ◽

Vol 26 (3-4) ◽

pp. 877-886 ◽

Cited By ~ 10

Author(s):

T. Ohtsuki ◽

M. Watanabe ◽

Y. Miyaji

Keyword(s):

High Performance ◽

Ph Dependence ◽

Granular Sludge ◽

Upflow Anaerobic Sludge Blanket ◽

Uasb Reactor ◽

Anaerobic Sludge ◽

Phase System ◽

Two Phase ◽

Start Up ◽

Initial Seed

Two start-up methods of thermophilic UASB reactor were investigated for fast start-ups; one utilized micro-carrier as an initial support material and the other used intact mesophilic UASB granules as an initial seed. With both methods thermophilic granules having high activity were obtained in less than 3 months, even with acidified wastewater. Maximum sludge load for VFA substrate and sugar substrate were 3.2 and 0.9 kgCOD/kgVSS/day, respectively. Pre-acidogenesis was indispensable for high-performance treatment of sugar-containing substrate. It was proven that with a two-phase system sludge load could be raised to 3.0 kgCOD/kgVSS/day for sugar containing wastewaters. Some features of obtained sludge were examined, including maximum substrate utilizing activities, temperature dependence, pH dependence, and activity deterioration under lower loading conditions.

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Influence of HRT (hydraulic retention time) and SRT (solid retention time) on the hydrolytic pre-treatment of urban wastewater

Water Science & Technology ◽

10.2166/wst.2001.0163 ◽

2001 ◽

Vol 44 (4) ◽

pp. 7-14 ◽

Cited By ~ 11

Author(s):

P. Ligero ◽

A. De Vega ◽

M. Soto

Keyword(s):

Retention Time ◽

Volatile Fatty Acids ◽

Oxygen Demand ◽

Phase Iii ◽

Urban Wastewater ◽

Solid Retention Time ◽

Start Up ◽

Pre Treatment ◽

Two Parameters ◽

Hydrolysis Of

This work presents the results obtained from a study on the pretreatment of urban wastewater using a digester that acted as a system for the retention of solids (sedimentation-filtration), hydrolysis of the retained solids and acidification of the dissolved substances. After start-up (Phase I), the digester was operated at hydraulic retention times (HRT) of 4.4, 3.4 and 2.2 h and at solid retention times (SRT) of 24, 16 and 14 d, during Phases II, III and IV, respectively. The retention and removal of suspended solids (SS) was maintained slightly above 60%, independently of HRT and SRT. Conversely, eliminated chemical oxygen demand (COD) decreased slightly upon reducing HRT and SRT. The influence of these two parameters on the generation of volatile fatty acids (VFA) is more notable, reaching effluent VFA concentration of 29 (Phase II), 96 (Phase III), and 107 (Phase IV) mg COD/l. VFA to SS generation ratios were 0.13 (II), 0.35 (III), and 0.48 (IV) g VFACOD/g SS added. Optimum values were reached at an HRT of 2.2 h. Taking 100 kg influent COD as a base, the conversion of different kinds of COD was as follows (in kg influent:kg effluent): VFACOD (4:17), non-VFA soluble COD (45:23), VSSCOD (51:23). Simultaneously to these conversions, 2 kg VSSCOD are generated as purge stream and 35 kg COD are eliminated during the process.

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