General Operating Conditions Research Articles

Dynamic Characteristics of LIT Girder Railway Bridges

This study analyzed the dynamic characteristics of railway bridges with low-weight, innovative truss (LIT) girders and evaluated their dynamic behavior under general and high-speed railway operating conditions. A dynamic analysis was performed considering various variables, including the span length (30, 35, 40, or 45 m), track (single or double), main girder type (three or five girders), track type (concrete or ballast), and train type (KTX, HEMU, freight train, Mugunghwa, or express EMU). The train load was modeled as a moving concentrated load, and the damping ratio was applied according to railway design standards. The results of the dynamic analysis showed that in most cases, railway bridges with LIT girders met the allowable criteria for vertical deflection, vertical acceleration, and warping. However, in the case of a 30 m span bridge, the vertical acceleration exceeded the allowable limit at a specific speed of the HEMU-430X high-speed train. The results of this study can be used to evaluate the applicability of LIT girders in railway bridges and provide useful information for future design and construction.

An Approach to Analyzing and Comparing the Cooling Performance of Two Indirect Evaporative Cooler Designs

Abstract Energy-efficient air cooling systems are always in demand. Direct evaporative coolers are energy-saving and have low cost, but in hot and humid areas, they produce an almost uncomfortable environment. Alternatively, modified indirect evaporative coolers with different technical configurations can produce better thermal output. This paper presents a simple thermodynamic approach developed to analyze, for comparison, the behavior of conventional and regenerative indirect evaporative coolers that comprise different process structures. The analysis is based on the energy balance of the coolers to consider which is more applicable for further modification. Similar performance cross-flow heat exchangers with separate air washers are adopted for both units. The two coolers are subjected to the same general summer operating conditions. The results showed that the conventional indirect evaporative cooler provided better cooling performance in terms of all thermal comparison parameters. The supply temperature trend in regenerative indirect evaporative cooler (RIEC) is higher by 23.4–34.1%, while its effectiveness is lower by 26–56% compared to that of the conventional indirect evaporative cooler (CIEC). The cooling capacity of CIEC is always higher at any air ratio value. At an equal secondary air flowrate where the primary air flowrate of RIEC is 25% more than that of CIEC, CIEC still generates lower air supply temperature and its effectiveness is higher. Thus, CIEC deserves priority attention for further development and additional improvement of performance.

An exploration of safety and feasibility of transoral vestibular endoscopy in the treatment of thyroid malignant tumors

Objective:To investigate the safety and feasibility of transoral vestibular endoscopy in the treatment of patients with thyroid malignant tumors. Methods:120 patients with thyroid cancer admitted to Xi 'an Central Hospital from January 2019 to December 2021 were selected and randomly divided into endoscopic surgery group（60 cases） and traditional open surgery group（60 cases）. The general operation conditions, postoperative complications and postoperative quality of life were compared between the two groups. Results:The intraoperative blood loss, indwelling drainage tube time and average length of hospital stay in the endoscopic surgery group were significantly lower than those in the traditional open surgery group （P<0.05）, while the operation time and number of lymph nodes dissected were significantly higher than those in the traditional open surgery group （P<0.05）. There was no significant differences in VAS score at 24h after surgery, white blood cell count, TgAb （+） and temporary hypothyroidism between the two groups at 24 h after operation （P >0.05）. The CRP, total drainage volume, TgAb and serum calcium in the endoscopic surgery group were higher than those in the traditional open surgery group, and the PTH and Tg were lower than those in the traditional open surgery group （P<0.05）.One case of hoarseness,2 cases of extremities numbness, 1 case of subcutaneous effusion and 2 cases of chin nerve injury occurred in the endoscopic surgery group, the total incidence of postoperative complications was 10.00%. Five cases of hoarseness, 11 cases of choking cough limbs numbness, 1 case of drinking water, 1 case of postoperative bleeding and 4 cases of subcutaneous effusion occurred in the traditional open surgery group, the total postoperative incidence of complications was 36.67%, the total incidence of complications in endoscopic surgery group was lower than that in traditional open surgery group （P<0.05）. The total scores of physiological status, social/family status, emotional status, functional status and quality of life in endoscopic surgery group were significantly lower than those in traditional open surgery group （P<0.05）. Conclusion:The application of oral vestibular endoscopy in the treatment of thyroid malignant tumors has the advantages of good surgical status and postoperative recovery, fewer postoperative complications.The patient was well tolerated,with positive safety，this technique has high clinical application value.

Mitigation of Performance Degradation of Cathodes for Polymer Electrolyte Membrane Fuel Cells

Polymer electrolyte membrane fuel cells (PEMFCs) are green energy conversion devices that convert chemical energy to electrical energy. Compared to other types of fuel cells, PEMFCs have various advantages including the low operating temperature, high power density, and short start-up times [1, 2]. However, the limited durability and high cost of platinum catalysts are the primary obstacles to the large scale commercialization of PEMFCs. Hence, a variety of scientific approaches have tried to improve the durability of Pt electrocatalysts as a main component of PEMFC membrane electrode assemblies (MEAs) [3]. Studies reported that the performance degradation of the catalyst layer in MEAs can be divided into the reversible and irreversible degradation processes. The first case is the permanent degradations caused by the platinum dissolution or corrosion of carbon support. It is well known results in PMEFC MEAs that carbon corrosion mainly occurs at operating conditions of higher than 1.0 V, whereas platinum agglomeration/dissolution happen at 0.6‒1.0 V. That is, the deterioration of platinum in the cathode is unavoidable under general PEMFC operating conditions of 0.6‒1.0 V [4, 5]. Numerous studies, such as tuning of platinum alloy composition and use of highly durable Pt-alloy catalysts have been conducted to suppress irreversible performance degradation [6-8]. In the reversible degradation phenomena, oxygen or hydroxyl groups are bonded to platinum in the cathode, which interferes with oxygen reduction reactions and reduces performance. However, even reversible degradation can result in permanent performance decay if not removed for a long time. Hence, researches on the strategies to mitigate reversible degradation are necessary to extend the lifetime of PEMFC MEAs. In particular, Pt-O film generated during operation is reversible and can be easily recovered by the periodical reduction of cathode potential [9, 10]. In this research, we develop the mitigation method to prevent performance degradation of MEAs during constant current operation. In addition, we quantitatively analyze the mitigation mechanism of MEAs via various physicochemical and electrochemical analysis tools.

A Retrospective Analysis on the Effects and Complications of Endoscope-Assisted Transoral Approach and Lateral Cervical Approach in the Resection of Parapharyngeal Space Tumors.

Objective To observe and compare the effects and complications of endoscope-assisted transoral approach and lateral cervical approach in the resection of parapharyngeal space (PSS) tumors. Methods From January 2013 to September 2021, 69 patients with parapharyngeal space tumors in the Affiliated Hospital of Jiangnan University were divided into the control group (n = 37) and the observation group (n = 32) according to the mode of operation. The tumors in the parapharyngeal space were resected by the lateral cervical approach in the control group, and the tumors in the parapharyngeal space were removed by endoscopy-assisted transoral approach in the observation group. The general clinical data and operation conditions of the two groups, including operative blood loss, operation time, drainage volume and drainage time, hospital stay, perioperative pain degree, and tumor resection rate were collected and analyzed statistically. The patients were followed up for 6 months, and the complications of the two groups were recorded. Results Compared with the control group, the operation time in the observation group was significantly shorter, and the amount of intraoperative bleeding in the observation group was significantly less than that in the control group, and the difference was statistically significant (P < 0.05). The postoperative drainage was less and the hospital stay in the observation group was shorter than that in the control group, and the difference was statistically significant (P < 0.05). There was no significant difference in tumor resection rate between the two groups. The visual analog scale (VAS) score on the 1st and 3rd day after operation in the observation group was lower than that in the control group. After treatment, some patients in the two groups had complications such as nerve injury, dysphagia, difficulty in mouth opening, massive hemorrhage, and parotid fistula. The total incidence of complications in the observation group was lower than that in the control group, and the difference was statistically significant (P < 0.05). Conclusions The effect of the endoscope-assisted transoral approach is similar to that of the lateral cervical approach in the resection of tumors in parapharyngeal space, but the endoscope-assisted transoral approach has shorter operation time, less intraoperative bleeding, and less postoperative drainage. The indwelling time and hospital stay of the drainage device were shorter than those of the patients with transcervical approach, and the perioperative stress response of patients with endoscope-assisted transoral approach is mild, which is beneficial to the physical and mental recovery of the patients.

Effects of short-segment pedicle screw internal fixation surgery combined with hyperbaric oxygen treatment for acute spinal injury on the morphology and function of the spine

To explore effect of short-segment pedicle screw internal fixation combined with hyperbaric oxygen in treating acute spinal fractures and its influence on recovery of spinal nerve function. A total of 96 patients with acute spinal fracture admitted from February 2017 to March 2020 were divided into combined group and control group, with 48 cases in each group. Both groups were treated with short-segment pedicle screw internal fixation. The combined group was given hyperbaric oxygen after surgery. The operation time, surgical blood loss, incision length and other general operation conditions between two groups were recorded. The differences in spinal morphology and function, Ameraican Spinal Injury Assiciation(ASIA) neurological function grade, serum inflammatory factors and ability of daily living activities were observed before and after surgery. There was no significant difference in operation time, surgical blood loss, and incision length between combined group and control group(P>0.05). There were no significant differences in anterior height ratio and Cobb angle between two groups before surgery, 1 week and 6 months after surgery(P>0.05). The height ratio of anterior margin of the injured spine was significantly improved in both groups at 1 week and 6 months after surgery compared with preoperative period (P<0.05), and Cobb angle was significantly reduced in both groups compared with preoperative period (P<0.05). There was no statistically significant difference in serum interleukin-6(IL-6), interleukin-8(IL-8), and tumor necrosis factor-α(TNF-α) levels between two groups at 1 d after surgery(P>0.05);the serum IL-6, IL-8, and TNF-α levels of combined group were lower than those of control group at 1 week after surgery (P<0.05). At 6 months after surgery, ASIA neurological function grade of combined group was C grade in 2 cases, D grade in 23 cases, E grade in 22 cases. In control group, 7 cases was grade C, 26 cases was grade D, 13 cases was grade E, and the difference between two groups was statistically significant(P<0.05). The Barthel score of combined group was higher than that of control group at 1 month and 3 months after surgery, and the difference was statistically significant (P<0.05);at 6 months after surgery, there was no significant difference in Barthel score between two groups(P>0.05). Short-segment pedicle screw internal fixation combined with hyperbaric oxygen for the treatment of acute spinal fractures is beneficial to the recovery of spinal nerve function after surgery, and has a certain effect on the early improvement of the patients' activities of daily living.

ML알고리즘을 이용한 종합병원의 공기감염균 분석

Recently, because of COVID-19 cases emerging due to the air conditioning system of buildings, the spread of infectious bacteria through indoor airflow is receiving continuous attention. Since the Outpatient Department maintains general air-conditioning operation conditions 20% outdoor-air and 80% recycled air, the exhaustion of infectious air currents is not fast enough at times when the number of visitors increases, which might lead to the nth infection. Due to this, in preceding research, the number of infectious bacteria depending on the number of visitors was predicted using ML algorithms. In this research, the characteristics and behavioral variables of visitors were applied to the algorithm used in the preceding research to predict once more the number of infectious bacteria based on the behavior of visitors. Also, the predicted number of infectious bacteria was used to analyze airborne infectious bacteria by room and by time of the day after categorizing the number of visitors into days of the week in which it is at its maximum, and days of the week in which it is at its minimum.BRThis research results are expected to be used as baseline data on air-conditioning system control algorithms that respond to changes in the number of visitors and infectious bacteria by room in the Outpatient Department.

Integrated Satellite-Terrestrial System Capacity Over Mix Shadowed Rician and Nakagami Channels

In this paper, we evaluate the ergodic capacity analysis of a integrated satellite-terrestrial cooperative communication system under independent and non-identical shadowed Rician and Nakagami-m fading channels. Multiple cooperative relay nodes are assumed between satellite and the destination node. Amplify-and-forward (AF) cooperative protocol is used at each fixed relay node for signal amplification. While for signals combining at the destination node, the maximum ratio combining(MRC) technique is exploited. An analytical approach is derived to evaluate the performance of the system in terms of ergodic capacity. We derive the approximate closed-form expression for calculating the ergodic capacity of the proposed system. It is shown that the derived analytical expression is very tight and applicable to the general operating conditions with the help of satellite channel date available from the literature. The analytical results are compared with Monte Carlo simulations, and they seem to agree well.

Nonlinear Dynamics in Mechanics: State of the Art and Expected Future Developments

AbstractStarting from a recent classification of the development stages of nonlinear dynamics in mechanics, this review builds on the idea that the level of scientific maturity of the area is now such as to involve a gradual shift of its core interests from the inherent theoretical and practical findings to the application benefits that they can bring to solving dynamic problems in a variety of technological environments. First, an overview of the current state of knowledge and the achievements of the community of relevant scholars in about the last ten years is presented, distinguishing between traditional and emerging themes fully inherent to mechanics, and more hybridized scientific contexts. Then, a “vision” of expected future developments is attempted, by organizing the presentation along some main lines. (i) Identifying modeling, methodological, and computational advancements needed to address challenging, new or updated, research issues, with a view to deepening and further expanding the ranges of theoretical development and practical interest of nonlinear dynamics. (ii) Overviewing directions toward which promoting full exploitation of intrinsic or intentionally added nonlinearities, to the aim of improving and possibly optimizing specific behaviors and general operating conditions of actual systems/structures in a variety of dynamic environments, by also referring to the uncertainty quantification issue. (iii) Pursuing “novel” lines of developments of nonlinear dynamics in a fully hybridized and cross-disciplinary framework, with also possible expectation of new related phenomenologies.

Effect of stator height change on bearing life in aircraft autopilot servos

PurposeThe purpose of this paper is to make a more precise prediction of the life of servo motors used in aircraft. The variation of the axial load created by the wave washer for bearing, which is one of the factors affecting the bearing life of the electric motors and servo motors used in aircraft, was analyzed.Design/methodology/approachIn electric motors and servo motors that body as stator, the height of the stator stack affects the compression amount of the wave washer spring. Working with electric motor and servo manufacturers, production-related variations in stator height were determined by making multiple measurements. The reaction forces resulting from these compression amounts were simulated by mathematical modeling with the finite element method, and also experimentally measured on real parts.FindingsResults obtained with finite element method and real experiments were compared. By adding the force differences to the general operating conditions, the effect on the bearing life was theoretically determined. In a servo motor with this type of construction, the difference in stator height created different axial loads on the motor shaft. The difference of these loads affected the motor bearing life.Research limitations/implicationsThe results implicated in terms of flight safety, maintenance operation and resource efficiency.Practical implicationsThe results of this study are effective in determining the maintenance intervals more clearly. This study can be used for the design criteria of aircraft servo motors. These servos, which are especially used to move the flight control surfaces, contribute to flight safety as the life expectancy will be clearer.Social implicationsThis study may be effective in preventing aviation accidents caused by servo motors. It can make maintenance management more efficient.Originality/valueThis study investigated the effect of aircraft servo motor design inputs on servo motor life, considering the production.

A retrospective analysis of emergency hysterectomy intervention strategy in obstetrics.

Objectives:To investigate the indications of obstetric emergency hysterectomy and analyze the clinical effects of subtotal hysterectomy and total hysterectomy.Methods:We included 247 hospitalized women who had undergone abdominal hysterectomy due to obstetric reasons in Fujian Province Maternity and Child Health Hospital (a provincial class-A hospital) and Ningde People’s Hospital (a primary Class-B hospital) between January 2002 and December 2018. We identified surgical indications and clinical characteristics of the patients. Furthermore, the patients from Fujian Provincial Maternity and Child Health Hospital were subdivided into subtotal hysterectomy group and total hysterectomy group to examine general operation conditions, and postoperative complications.Results:The main surgical indications for emergency obstetric hysterectomy in Fujian Maternity and Child Health Hospital were placental implantation (49.6%) and uterine weakness (31.9%), while uterine weakness (37.5%) was the most important indication in Ningde People’s Hospital. No differences were found in operation time, hospitalization time, intraoperative blood loss, postpartum blood loss, and intraoperative fresh frozen plasma transfusion between the subtotal hysterectomy group and the total hysterectomy group. Postoperative test parameters, including postoperative prothrombin time (PT), thrombin time (TT), activated partial thromboplastin time (APTT), hemoglobin (HGB), and hematocrit (HCT), were not significantly different between the two groups. No significant difference was noted in postoperative vesicoureteral injury, pelvic hematoma, infection, and disseminated intravascular coagulation (DIC) incidence, but renal failure incidence was different (P=0.040).Conclusion:The treatment effect of subtotal hysterectomies for the cases without placenta accreta and placenta previa was similar in the two hospitals. There is no statistically significant difference in therapeutic effect between total hysterectomy and subtotal hysterectomy.

Protecting building occupants against the inhalation of outdoor-origin aerosols

During normal operations, buildings can protect their occupants from outdoor airborne particle hazards of all types, including airborne pollutants. A long-term international research effort has advanced our knowledge of building protection physics. Recently we have developed an operationally efficient, regional-scale methodology - Regional Shelter Analysis - to account for both building protection effects and the typical distribution of people in and among buildings. To provide input to this capability, we estimate here the degree of protection afforded by the currently existing US building stock. We first assemble and summarize the published literature relevant to indoor particle losses including (a) deposition to indoor surfaces, (b) losses that occur when particles penetrate through the building envelope, and (c) heating, ventilation and air conditioning (HVAC) system filtration efficiencies as well as general building operating conditions. Building protection against inhaling particulate hazards varies strongly, by orders of magnitude, according to particle size, airborne particle loss rate, and to a lesser extent building use (occupancy). Protection increases modestly as particle size increases from 0.1 to 1 μm and significantly as particle size increases from 1 to 10 μm. Model results are placed in context with previously reported measurements. Suggestions for future work, including enhanced validation datasets are provided.

Nanoparticles: Untying the Gordian Knot in Conventional Computed Tomography Imaging

X-ray computed tomography (CT) imaging plays an essential role in disease diagnosis due to its noninvasive, painless mode and superior penetration depth. However, the resolution of the soft tissue ...

Experimental study and quantum chemical calculation of free radical reactions in p-nitrophenol degradation during electrochemical oxidation process

Electrochemical oxidation process (EOP) has received attentions in wastewater management in recent years. However, high electrodes cost and low current efficiency have challenged the industrial application. Therefore, dimensional stable anodes (DSA) are developed due to relative low price and high efficiency of chlorinated active species generation. However, with low concentration of mediums, the direct oxidation still plays the main role in the organic pollutants degradation, resulting in low current efficiency of process. Thus, in this study, the impact of general operating conditions including type of electrolyte, active species addition, pH and current density on proportion of direct and indirect oxidation during p-nitrophenol degradation in DSA system have been studied, trying to enhance the contribution of indirect oxidation. The contribution was measured by scavenging tests. It concluded that low pH and adding NaClO can improve the contribution of indirect oxidation, but extra H2O2 significantly hindered the PNP degradation. Furthermore, we have studied the behaviors of free radical reactions by quantum chemical calculation. Three mechanisms including hydrogen atom transfer (HAT), radical adduct formation (RAF) and electron transfer (ET) were discussed in hydroxyl free radical and chlorine-derived radicals reactions. According to calculated thermodynamic and kinetic parameters, it indicated that active sites in primary reactions initiated by OH are significantly more than that in chlorine-derived radical reactions, corresponding to the differences of experimental phenomenon under different mediums. Degradation pathways and main byproducts formation were also proposed. We provided an insight to study oxidation mechanisms of EOP by means of experiments combining quantum chemical calculation.

Investigation of the Gas-Liquid Flow in an Agitated Vessel Equipped with an ASI Impeller by Using Tomography Method

In this study, the hydrodynamics of the gas dispersion in an aerated vessel equipped with a newly designed impeller (ASI impeller), a combination of the pitched blade turbine and the Scaba impeller was investigated. The performance of the ASI impeller was compared with the performances of the pitched blade turbine and the Rushton impeller. The non-invasive Electrical Resistance Tomography (ERT) technique was used to assess the gas dispersion inside the mixing vessel. The effects of the volumetric gas flow, and impeller type and speed were investigated on power drawn, gas holdup, and mixing time. An analysis of the experimental data indicated that the ASI impeller exhibited a minimal effect of the gassing on the power drawn compared to the pitch blade and the Rushton turbine. Measured data on gassed power consumption indicated that the ASI impeller was about 45% more efficient than the Rushton turbine and 20% more than the downward PBT under the general operating conditions in bioreactors for gas flow rate about 1 vvm. Also, this impeller showed a higher amount of gas hold up and lower mixing time compared to the two other studied impellers. A dimensionless correlation for the relative power consumption as a function of flow number and Froud number was developed for the aerated agitated tank. Also, a dimensionless correlation was introduced to compute the overall gas hold up as a function of specific power consumption and superficial gas velocity for the gas-liquid agitated system. The overall conclusion from this study demonstrated that the axial-radial ASI impeller is a good energy-efficient impeller for the aeration system and bioreactors based on the results from the investigation of the data in terms of the power consumption, gas holdup, and mixing time.

Application of dexmedetomidine-assisted intravertebral anesthesia in hip replacement and its influence on T-lymphocyte subsets.

Application of dexmedetomidine-assisted intravertebral anesthesia for elderly patients with hip replacement and its influences on T-lymphocyte subsets in peripheral blood were assessed. Eighty-six patients undergoing intravertebral anesthesia in hip replacement were treated as group A, and one hundred patients undergoing intravertebral anesthesia combined with dexmedetomidine were treated as group B. Hemodynamic changes in both groups were compared 5 min before anesthesia (T0), immediately after skin incision (T1) and after surgery (T2). General operation conditions of patients in both groups were recorded. T-lymphocyte subsets, interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), visual analogue scale (VAS) pain scores and mini-mental state examination (MMSE) cognitive function changes before surgery and 24 h after surgery were compared between the groups, and the incidence of complications in both groups after 24 h was recorded. The recovery time of patients in group B was shorter than that of group A (P<0.05). Changes of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate fluctuations in group B were lower than those in group A (P<0.05). At 24 h after surgery, VAS scores of group B were lower than those of group A (P<0.05); levels of IL-6 and TNF-α were lower than those of group A (P<0.05); CD3+ cells, CD4+ cells, CD8+ cells, and CD4/CD8 ratio were higher than those of group A (P<0.05), and MMSE score was higher than that of group A (P<0.05). The incidence of gastrointestinal reactions and postoperative cognitive dysfunction (POCD) in group B was lower than that in group A (P<0.05). In conclusion, administration of dexmedetomidine can effectively shorten the recovery time of patients, stabilize intraoperative hemodynamics of patients, protect immune function, and reduce postoperative pain and POCD occurrence during anesthesia of hip replacement.

Balancing Fairness and Efficiency: Performance Evaluation with Disadvantaged Units in Non-homogeneous Environments

Balancing fairness and efficiency has become an emerging issue in today's society. In this paper we propose a balanced benchmarking methodology to address the fairness issue in performance evaluation. The methodology used to create performance measures is data envelopment analysis (DEA), a tool designed to evaluate the relative efficiencies of comparable decision-making units (DMUs); i.e. all DMUs use the same inputs and outputs and experience the same general operating conditions. In many applications, however, the DMUs may experience non-homogenous operating conditions or environments. An example might be a set of manufacturing plants where some have been upgraded and others not. Such settings can necessitate modifying the DEA structure such as to make allowance for different environmental conditions. Such a model is developed herein to create a level playing field for performance evaluation in two different settings: a setting involving hybrid and conventional (non-hybrid) vehicles; and another setting involving bank branches located in poverty and non-poverty regions. Our model and empirical tests contribute not only to the advance of balanced benchmarking methodologies, but also to the practice of incorporating fairness in performance evaluation across multiple products and organizations.

Study on the performance of a novel waste heat recovery system at low temperatures

A novel system for recovering waste heat is investigated, consisting of an auto-cascade cell and working fluids of tetrafluoro-ethane (R134a)/trifluoro-methane (R23)/dimethylformamide (DMF). For the novel system, reliable models are developed by applying thermodynamic principles and the Peng–Robinson equation of state. The main factors are discussed from broader insights that affect the performance of the novel system. It is found that there is an optimal generating pressure and composition of R134a/R23 mixtures to obtain a maximum coefficient of performance (COP), which are affected, not only by generating, condensing, and evaporating temperatures, but also by absorption temperatures. Under general operational conditions, the maximum COP ranges from 0.048 to 0.1093, and the optimal mole ratio of R23 to R134a ranges from 0.29 to 0.41. Moreover, the experimental refrigeration temperature reaches −62.3 °C and the COP is 0.023, with an enhancement of 30%, which corresponds to an optimal generating pressure of 1130 kPa and a mole ratio of 0.3. Through the theoretical and experimental results, it is demonstrated that mass and energy coupling of refrigerants in the auto-cascade cell has key effects on the performance. It also shows that refrigeration temperatures could be lowered, and that COP is improved by staged double absorbers.

Artificial Intelligence-Based Emission Reduction Strategy for Limestone Forced Oxidation Flue Gas Desulfurization System

Abstract The emissions from coal power plants have serious implication on the environment protection, and there is an increasing effort around the globe to control these emissions by the flue gas cleaning technologies. This research was carried out on the limestone forced oxidation (LSFO) flue gas desulfurization (FGD) system installed at the 2*660 MW supercritical coal-fired power plant. Nine input variables of the FGD system: pH, inlet sulfur dioxide (SO2), inlet temperature, inlet nitrogen oxide (NOx), inlet O2, oxidation air, absorber slurry density, inlet humidity, and inlet dust were used for the development of effective neural network process models for a comprehensive emission analysis constituting outlet SO2, outlet Hg, outlet NOx, and outlet dust emissions from the LSFO FGD system. Monte Carlo experiments were conducted on the artificial neural network process models to investigate the relationships between the input control variables and output variables. Accordingly, optimum operating ranges of all input control variables were recommended. Operating the LSFO FGD system under optimum conditions, nearly 35% and 24% reduction in SO2 emissions are possible at inlet SO2 values of 1500 mg/m3 and 1800 mg/m3, respectively, as compared to general operating conditions. Similarly, nearly 42% and 28% reduction in Hg emissions are possible at inlet SO2 values of 1500 mg/m3 and 1800 mg/m3, respectively, as compared to general operating conditions. The findings are useful for minimizing the emissions from coal power plants and the development of optimum operating strategies for the LSFO FGD system.

The Ultimate Noise Limit for Hall Plates in Voltage, Current, and Hybrid Operating Modes

If Hall plates are used as magnetic field sensors they are usually powered up by a current source connected to a pair of non-neighboring contacts. The output voltage is tapped at another pair of non-neighboring contacts. In this paper we study more general operating conditions of Hall plates with an arbitrary number of contacts. In such hybrid operating modes current sources are connected to a first set of contacts and voltage sources to a second set of contacts. Output voltages are tapped at the first set of contacts and output currents are measured at the second set of contacts. All these output signals are multiplied by coefficients and added up. The purpose of this work is to figure out which operating mode and which Hall plate achieve maximum signal at minimum thermal noise and power dissipation. To this end we develop a theory, which gives the ratio of signal over noise and power as a function of the resistance matrix of Hall plates, of the supply voltages and currents, and of the coefficients. Optimization is done analytically in closed form and numerically for specific examples. The results are: 1) all operating modes have identical noise performance if their parameters are optimized; 2) for any Hall plate one can measure its resistance matrix and insert its values into our formulae to obtain the optimum supply currents and coefficients for optimum noise performance.