Coefficient Of Variation Values Research Articles

Population Size Limits the Coefficient of Variation in Continuous Traits Affected by Proportional Copying Error (and Why This Matters for Studying Cultural Transmission)

The accumulated copying error model (ACE) combines findings on the proportional nature of human visual perception error with cultural transmission theory. Previous studies have employed ACE to provide population-level expectations of the coefficient of variation (CV) of a continuous trait, such as the thickness of ceramic vessels. To date, empirical departures from expected CV values have been interpreted as evidence of biased cultural transmission or functional constraints without consideration for how population size might affect population-level cultural variation in the presence of proportional perception error. Here, I employ agent-based simulation experiments to investigate the ways in which population size affects the CV of a continuous cultural trait under different cultural transmission mechanisms. Results show that the CV of a continuous cultural trait is a function of its cultural equivalent N and effective population size (Ne) as well as the relative strength of cultural selection. The results also demonstrate that different combinations of N and cultural transmission yield identical CV values. The study highlights a new set of difficulties with inferring individual-level process—the mechanism(s) by which cultural information is transmitted among individuals—from population-level pattern—the CV of a continuous cultural trait. In light of these results, I identify and discuss one avenue through which we might improve our ability to infer past cultural transmission from archeological data.

Effect on Sorghum Yield in The Semi-Arid Counties of Lower Eastern Kenya's

Sorghum is a key crop in Kenya's attainment of food and nutrition security. Climate is a key determinant of sorghum production under rainfed conditions. The overall objective of this study was to examine variations of sorghum yields in response to climate. This is crucial in documenting future strategic options to enhance food security in a changing climate. A longitudinal research design was used in the study. Purposive and cluster sampling techniques were used to select sorghum and climate data from lower eastern Kenya's districts covering the period 1979-2009. Association between sorghum crop yields and climate data were sought through correlation analysis, while variability in yields was determined through the coefficient of variation (CVs) and standard deviations (STDEV). There wide sorghum yield and climate variability with high CV values of up 60 % of rainfall. Kitui had the lowest variation in sorghum yields with a Standard deviation of 344.1 Kg/Ha (CV = 38.7 %) while Machakos had the highest variation with STDEV of 591.6 Kg/Ha (CV = 60.5 %). This information is useful to monitor and forecast future sorghum production under rain-fed agriculture. There is a need to continue with focused applied research to unleash sorghum's capacity to be the cornerstone of food security in Kenya.

Test-retest Reliability Of Various Methods For Body Composition Assessments

Multi-compartment body composition assessment techniques are common in research and for assessing intervention success. Establishing the validity and reliability of assessment techniques help to ensure appropriate outcomes. PURPOSE: To identify the intra (same day) and inter (between-day) test-retest reliability of BIA, BIS, and DEXA composition assessments conducted on two consecutive days in a healthy population. METHODS: 40 healthy, collegiate-aged participants (male: n=20; 24.6 ± 4.1yr, 177.5 ± 6.7 cm, 88.1 ± 13.3 kg; female: n=20; 22.8 ± 4.5 yr, 163.6 ± 6.5 cm, 64.6 ± 14.3 kg) completed two study visits with 24 hours. All participants arrived fasted (10 h) and after abstaining from exercise (24 h). Each visit consisted of two consecutive rounds (four total measurements) of assessments including body weight, BIA (InBody 570), DEXA scan, and BIS. Pearson correlations, intraclass correlation coefficient (ICC), coefficient of variation (CV), and standard error of the mean (SEM) were computed to assess relationship and reliability between measurement techniques. A p-value of 0.05 was used to assess all statistical outcomes. RESULTS: Intra-test and inter-test ICC, CV, and SEM values for all three measurement techniques are provided in table 1. Strong, positive correlations between BIA vs DEXA FM (r = 0.95), DEXA vs BIS FM (r = 0.89), BIA vs DEXA FFM (r = 0.99), and DEXA vs BIS FFM (r = 0.96) were observed. CONCLUSION: All three methods yielded high intra- and inter-test retest reliability with strong correlations between measurements and excellent CV and ICC values suggesting good repeatability with the largest variation being observed for BIS FM and FFM.Table 1: ICC, CV, and SEM values for BIA, DXA, and BIS analysis

Total Errors of TSH results by fluorescent immunoassay technique from dried blood spots in a newborn screening program for congenital hypothyroidism - variations in time

Abstract Objective:the aim of this study was to evaluate the imprecision of the method used to determine TSH (Thyroid Stimulating Hormone) levels from dried blood spots in a newborn screening program and how the value of the coefficient of variation influences the total error of the method. Methods:A short-term evaluation of imprecision was compared with the imprecision of the method assessed over five years. The coefficient of variation from the best quality control period and the worst quality control period were used. For Bias assessment mean results from the external quality program were used. Total Error was calculated with Bias and Coefficient of Variation values. A freely available software was used for standard deviation and coefficient of variation profiling. Results:The values of the coefficient of variation for the short-term were lower than values obtained in worst quality control period but higher than in the best quality control period. Total error was higher than the accepted value for low-level control in the worst quality control period. Images obtained with the software showed that for high-level control coefficient of variation is concentration-dependent but this finding is not similar for low-level control. Conclusions:Total Error of the Method may be subject to change in time. Initial evaluation of imprecision must be performed on a short term analysis but a continuous evaluation should be performed as the performance of a method may change in time. The evaluation should be performed on clinically significant levels for each parameter.

PENETAPAN KADAR TOTAL FLAVONOID EKSTRAK ETANOL KACANG MERAH (Phaseolus vulgaris L.) SECARA SPEKTROFOTOMETRI VISIBEL

Red kidney bean is one of the string bean that contain highest fiber with concentration 26,3 gram/100 gram substance. Red kidney bean contains flavonoid tannin steroid/triterpenoid and kumarin. Flavonoid in red kidney bean has antidiabetes activity. This research aims to determine total flavonoids content in the red kidney bean extract. Extraction is done using maceration method with 70% ethanol solvent. The extract which is got is used for qualitative and quantitative analysis. Quercetin used as a standard solution. Qualitative analisys using TLC, Wilstater Cyanidin method, and qualitative analisys using aqueous NaOH. Quantitative analysis using Visible Spectrophotometry on a wavelength of 430.0 nm and operating time at the 27th minute. The results of qualitative test showed that the extract was positive flavonoids. The average concentrations of total flavonoids was 0,4733% extract with a variation coefficient value of 1,2%.

Study of Initial Material of Vetch

The study was conducted in the experimental field of the Institute of Forage Crops – Pleven, Bulgaria for a three-year period. Ten vetch specimens (varieties and populations) different originated were examined – Bulgarian population (Vicia sativa); Bulgarian population (Vicia pannonica ssp. striata; Detenicka Panonska (Vicia pannonica) and Asko 1; Kowatschite, K- 25 331, K- 29 800, K- 30 553, K- 30 574, K- 30 671 from Vicia villosa. The main quantitative characteristics were analyzed: plant height (cm), height of the first pod (cm), number of pods per plant, number of seeds per plant, number of seeds per pod, weight of seeds per plant (g) and indicators: beginning of flowering stage (days) and duration of the growing season (days). Two-way ANOVA and variance analysis were used for statistical data processing. High values ​​of variation coefficient were found for seed weight (107.87%), number of seeds per plant (88.80%), height of first pod (30.78%), number of pods per plant (37.97%) and number of seeds per pod (27.45), and average variation for plant height (15.97%), respectively. The varieties of Vicia pannonica can be characterized as early ripening with a growing season duration of 244-246 days, the population of Vicia sativa as medium ripening (242-252 days), and from Vicia villosa (except K-29 800, Kowatschite and Asko 1) as late maturing (242-256 days). The varieties of the species Vicia villosa K-30 671, Asko and 1 K-25 331, which are well leafed and form long stems (142-151 cm), are suitable as parental components in the combinational selection in the direction for forage. The Bulgarian population of Vicia sativa was found to form the largest number of both, pods (87) and seeds (351). For other the numbers, the seeds per plant trait was between 116 (K-30 574) and 133 (K-30 553). In the direction of seed production the Bulgarian population of Vicia sativa can be emitted.

A low coefficient of variation in hepatic triglyceride concentration in an inbred rat strain

BackgroundInbred strains are characterized by less genetic variation, which suggests usefulness of inbred strains for evaluations of various parameters. In this study, experimental reproducibility in several parameters was compared between an outbred Wistar rat and Wistar King A Hokkaido (WKAH/HkmSlc) rat, the inbred strain that is originated from Wistar rats.MethodsDifference of variations was investigated in parameters of body compositions and liver functions such as body weight, liver weight, liver triglycerides (TG), liver cholesterol and plasma alanine aminotransferase activity (ALT) between WKAH rats and outbred Wistar rats by using the coefficient of variation (CV).ResultsThere was no difference in the CVs of body weight and relative liver weight between WKAH and Wistar rats. The CVs of body weight and relative liver weight were below 10% in both WKAH and Wistar rats. The CVs of TG, cholesterol, and ALT in Wistar rats were between 30 and 40%, whereas those in WKAH rats were between 10 and 25%. A low CV level of TG was observed in WKAH rats compared to that in Wistar rats regardless of the duration of the experimental period in those rat strains.ConclusionThe low CV values in metabolic parameters involved in liver functions in the inbred rats suggested an advantage of using inbred rather than outbred rats for the evaluation of liver lipid metabolism.

Experimental study on dynamic injection behaviors of biodiesel and its blends in a common-rail injection system

The dynamic injection behaviors of pure biodiesel, high-proportioned biodiesel blends, and low-proportioned biodiesel blends in a common-rail injection system are researched. The effects of biodiesel ratio in the blended fuel and injection condition on the injection rate, cycle injection quantity, and fuel line pressure at the injector inlet are determined. The findings show that the injection duration is extended with the decrease in biodiesel ratio in the blended fuel, and fluctuation amplitude of injection rate in the stable injection stage increases. The first four pressure peaks for pure biodiesel decrease rapidly, while for blends, they decrease slowly, which results in an increasing difference of four pressure peaks between pure biodiesel and blends. With the decrease in biodiesel ratio, the mean volume injection quantity for three fuels gradually increases in the same injection condition. The coefficient of variation of the cycle injection quantity value for biodiesel and its blends with 30 cycles increases. The coefficient of variation value for biodiesel is between 0.4% and 0.7%. Compared with pure biodiesel, the mean volume injection quantity for BD70 increases by about 20–32%, and the coefficient of variation value is between 0.7% and 1.7% for high-proportioned biodiesel blends. The mean volume injection quantity increases by about 36–43% for low-proportioned biodiesel blends and the coefficient of variation value is between 1.1% and 2.1%.

Importance of standardizing the number of cells measured for coefficient of variation (COV) estimates of corneal endothelial cell area values as relevant to contact lens wear

PurposeTo assess the impact of using different numbers of cells in calculations of the coefficient of variation (COV) value for normal and polymegethous endothelia MethodsFour sets of 20 non-contact specular microscope images obtained from Caucasian individuals were assessed, and categorized according to the extent of polymegethism, i.e. grade 0 (none), grade 1 (mild), grade 2 (moderate) and grade 3 (substantial). Cell areas were measured manually and then values for between 2 and 100 cells were progressively added and averaged to generate COV estimates. These were then assessed in terms of their relative values (as percentages +/- SD) in relation to the value obtained on over 100 cells. ResultsFor the 4 sets of endothelia with group-mean COV values of 25.8, 33.1, 45.1 and 56.8%, the reliability of the COV estimates realized asymptotic values of close to ±1.0, ±2.7, ±3.6 and ±5.0% with 90 cells, but with greater uncertainty with few numbers of cells, e.g. only to within ±3.4, ±5.3, ±6.1 and ±7.9% with 75 cells. ConclusionsCOV estimates for the corneal endothelium are dependent on the number of cells used in the calculations. It is recommended that every effort should be made to not only assess 75–100 cells per endothelial image, but that this number should be the same or very similar for all endothelial images in a particular data set so that the uncertainly (or estimated proportional error) in the estimates is balanced.

Precision of autoantibody assays in clinical diagnostic laboratories: What is the reality?

BackgroundISO 15189 accreditation remains a challenge for specialized laboratories. In the field of autoimmunity, beside the crucial problem of absence of standardization, laboratories have to manage the analytical performances of the large panel of assays in terms of sensitivity and specificity, but also on their measurement precision for which no reference values are available on biorepositories. MethodsAs an initiative of the French EASI (European Autoimmunity Standardization Initiative) group, French clinical diagnostic laboratories were requested to participate in a survey aiming to analyze the coefficients of variation (CVs) of intra-run and inter-run variability obtained with assays quantifying 14 different autoantibodies. Two performance goals corresponding to the 90th percentile and the 50th percentile (lowest CV values reached by 90% and 50% of laboratories respectively) defined for three levels of concentration were calculated. The impact on the assay performances of the number of measurements, of the nature of the internal quality control (IQC) and the type of immunoassay, was also analyzed. Results414 and 616 values of intra-run and inter-run CVs were collected, respectively. The 50th percentile performance goals were comprised between 1.0% and 8.9% for the intra-run CVs, and between 1.8% and 14.6% for the inter-run CVs. At 90th percentile, the performance goals were comprised between 3.2% and 13.5% for the intra-run CVs, and between 7.3% and 30.8% for the inter-run CVs. CVs calculated from 10 values were similar to those obtained from more values. Higher imprecision was observed when the antibody levels of the IQC was lower than 2 fold the positive threshold. Commercial IQCs gave lower CVs than IQCs derived from patient samples. ConclusionOur results allow proposing some acceptability limits for the precision performances of the autoantibody assays, compatible with the reality of life in diagnostic laboratories and clinical care.

916-P: Precision Evaluation of Clinical Laboratory Glucose Reference Systems

Background: In response to the discontinuation of the industry standard YSI 2300 STAT PLUS glucose analyser Lifescan, as a major manufacturer of blood glucose measurement systems, initiated a comparative evaluation of currently marketed point of care (POC) glucose measurement devices to identify a potential replacement comparator system within a clinical environment. Method: Four POC devices were selected for in-depth assessment. Glucose measurement precision is a key performance metric for a comparator device, with higher standard deviation and coefficient of variation values imparting greater measurement uncertainty to diabetes test systems. This laboratory assessment used venous whole blood samples collected in Lithium Heparin coated tubes and tested within 12 hours of blood draw. All potential sources of variation such as donor and operator were controlled to give a best-case indication of performance. Results: Precision data were generated for the YSI 2300 STAT PLUS and four POC devices. 20 replicates were obtained per device at each of four glucose concentrations (50, 100, 200 and 500 mg/dL). The Abbott i-STAT Alinity (using CG8+ cartridge) demonstrated consistently lower standard deviation and coefficient of variation values when compared to the YSI 2300 STAT PLUS and other tests systems. Conclusions: A comparison of four currently marketed POC devices indicated that only one demonstrates precision performance that is equivalent or better than the YSI 2300 STAT PLUS across a wide range of glucose concentrations and thus is a strong candidate as a replacement clinical comparator system. Disclosure S. Phillips: Employee; Self; LifeScan, Inc. Employee; Spouse/Partner; LifeScan, Inc. S.J. Setford: Employee; Self; LifeScan Scotland. D.M. Shearer: None. A. Smith: Employee; Self; LifeScan, Inc. J.N. Ross: Employee; Self; LifeScan, Inc.

Comparison of Endothelial Cell Density, Morphological Changes and Central Corneal Thickness after Phacoemulsification between Diabetic and Non-Diabetic Patients

Background: Corneal endothelial tissues are susceptible to mechanical trauma from ultrasound energy during phacoemulsification. Several studies have reported various results of phacoemulsification effect on corneal endothelial cells between diabetic and non-diabetic patients. Purpose: To compare endothelial density, hexagonality, Coefficient of Variance (CV) and Central Corneal Thickness (CCT) changes between diabetic and non-diabetic patients at four weeks after phacoemulsification. Methods: Specular microscopy examinations prior to phacoemulsification and at four-weeks after phacoemulsification were performed on diabetic and non-diabetic groups with cataract. Later, patients in the diabetic group were divided based on their HbA1c level. The changes in endothelial density, the percentage of hexagonality, CV and CCT were evaluated. Results: At a four-weeks follow up, there were no statistical differences in endothelial cells density, CV and CCT changes between diabetic and non-diabetic groups. Mean (SD) of hexagonality percentage at four weeks of follow-up was lower (p-value=0.001) in diabetic group [(14.6) 41.7%] compared to non-diabetic group [(14.5) 50.1%]. There were no differences in endothelial cells density, hexagonality, CV and CCT values between the diabetic group with HbA1c level <7.5% and HbA1c level ≥7.5% at 4-weeks after phacoemulsification. Conclusion: There were no statistically significant differences in the endothelial loss, reduction of CV and CCT changes between the diabetic and non-diabetic group at four-weeks follow up after phacoemulsification. Diabetic group showed greater hexagonality decrease compared to non-diabetic group at four weeks after phacoemulsification. Different HbA1c levels did not affect the changes in endothelial density, the percentage of hexagonality, CV and CCT after phacoemulsification.

Performance characteristics of Fungitell STAT™, a rapid (1→3)-β-D-glucan single patient sample in vitro diagnostic assay.

Serum (1→3)-β-D-glucan (BDG), is an adjunct test in the diagnosis of invasive fungal disease (IFD). Fungitell STAT™, a facile, rapid, single patient option, executable for one or more patient specimens in approximately an hour, has been developed to address a need for rapid in-house testing. This method presents qualitative information concerning serum BDG levels, using an index value that allows the rapid categorization of patients as positive, negative, or indeterminate relative to serum BDG titer. The categorical and analytical performance of Fungitell STAT was evaluated. The categorical agreement between methods was established by testing patient samples which had been previously categorized with Fungitell. Receiver Operating Characteristic curves were used to identify cut-offs using 93 de-identified patient specimens. Subsequently, using these cutoffs, an independent group of 488 patient specimens was analyzed. Positive percent agreement (PPA) with, and without, indeterminate results was 74% and 99%, respectively. Negative percent agreement (NPA) was 91% and 98% with, and without, indeterminate results, respectively. Additionally, commercially available normal off-the-clot sera were spiked with Saccharomyces cerevisiae-derived (1→3)-β-D-glucan to produce analytical samples. Analytical reproducibility using spiked samples was excellent with 94% of the CV (coefficient of variation) values ≤10% among three independent laboratories. Good correlation with the predicate method was demonstrated with correlation coefficients of 0.90 or better with patient samples and 0.99 with spiked samples. The Fungitell STAT index assay provides a rapid and suitable method for serum BDG testing.

Evaluation of engine efficiency, emissions and load range of a PPC concept engine, with higher octane and alkylate gasoline

Gasoline Compression Ignition research has shown that it can provide diesel like engine efficiency while maintaining gasoline like exhaust emissions. While research has shown that lower octane fuels might be good for that, they are also not available now. A good compromise for that would be the use of higher octane gasoline which is available in most places.For this study, experiments were performed under Partially Premixed Combustion (PPC) conditions with RON 90 gasoline, in a 2 L multi-cylinder diesel engine which complies with Euro 6 emissions standards. The aim is to evaluate the efficiency, the emissions and the achievable load in terms of minimum and maximum at three different speeds, 1200, 1800 2400 rpm and with two different RON 90 gasolines and the standard diesel engine hardware. The two fuels were a regular pump gasoline and an alkylate gasoline, which was chosen to represent a pathway to a renewable fuel. Results show that the minimum load is around 5 bar IMEPg, limited by high COV (coefficient of variation) values and high air intake temperature, while the maximum load reaches 18 bar IMEPg, limited by lambda value, pressure and mechanical limitations. While efficiency is similar between the two fuels with a brake value of around 40%, at higher loads the alkylate fuel produces higher amounts of soot while the regular gasoline has higher carbon monoxide at low loads. Finally, an energy balance comparison between the two gasolines and diesel is made, showing improved efficiency and soot emissions under PPC.

Determining the reliability and usability of change of direction speed tests in adolescent female soccer players: a systematic review.

This review aimed 1) to describe the most common tests used for assessing change of direction (COD) performance; 2) to detail the reliability of current COD tests; 3) to provide an overview of current intervention strategies used to improve COD performance in adolescent female soccer players. A computerized search was conducted in the PubMed, Cochrane Plus and Web of Science (from 1995 to January 2020) for English and Spanish language and peer-reviewed investigations. A total of 221 studies were identified, with only 16 meeting the specific search criteria. The main findings were that eleven different tests have been used to assess COD performance with intraclass correlation coefficient and coefficient of variation values between 0.72-0.99 and 1-10.6%, respectively. The number of CODs performed during each test ranged from 1 to 9 within a range of 45º to 180º and with a duration <5 s, 5-9 s and >10 s. Findings indicate that the reliability of the COD tests seems to depend on: the equipment used, the surface tested on and the technical level of the soccer player. These results should be interpreted with caution as they may be influenced by the period of growth and maturation, the playing position of the player and the period of the soccer season. Finally, strength and power drills could be considered as appropriate to improve COD performance.

Association of glucose variability at the last day of hospitalization with 30-day readmission in adults with diabetes

ObjectiveTo evaluate whether increased glucose variability (GV) during the last day of inpatient stay is associated with increased risk of 30-day readmission in patients with diabetes.Research design and methodsA comprehensive...

Machine learning ensemble modelling as a tool to improve landslide susceptibility mapping reliability

Statistical landslide susceptibility mapping is a topic in complete and constant evolution, especially since the introduction of machine learning (ML) methods. A new methodological approach is here presented, based on the ensemble of artificial neural network, generalized boosting model and maximum entropy ML algorithms. Such approach has been tested in the Monterosso al Mare area, Cinque Terre National Park (Northern Italy), severely hit by landslides in October 2011, following an extraordinary precipitation event, which caused extensive damage at this World Heritage site. Thirteen predisposing factors were selected and assessed according to the main characteristics of the territory and through variance inflation factor, whilst a database made of 260 landslides was adopted. Four different Ensemble techniques were applied, after the averaging of 300 stand-alone methods, each one providing validation scores such as ROC (receiver operating characteristics)/AUC (area under curve) and true skill statistics (TSS). A further model performance evaluation was achieved by assessing the uncertainty through the computation of the coefficient of variation (CV). Ensemble modelling thus showed improved reliability, testified by the higher scores, by the low values of CV and finally by a general consistency between the four Ensemble models adopted. Therefore, the improved reliability of Ensemble modelling confirms the efficacy and suitability of the proposed approach for decision-makers in land management at local and regional scales.

Detection of bovine viral diarrhea virus genotype 1 in aerosol by a real time RT-PCR assay

BackgroundAs a pestivirus of the Flaviviridae family, bovine viral diarrhea virus (BVDV), has imposed a large burden on animal husbandry worldwide, and such virus can be transmitted mainly through direct contact with other infected animals and probably via aerosols. In the present study, we aimed to develop a real-time RT-PCR method for detection of BVDV-1 in aerosol samples.MethodsA pair of primers specific for highly conserved regions of the BVDV-1 5′-UTR was designed. The standard curve and sensitivity of the developed assay were assessed based on 10-fold serial dilutions of RNA molecular standard. The specificity of the assay was evaluated with other pestiviruses and infectious bovine viruses. The clinical performance was examined by testing 169 aerosol samples.ResultsThe results showed that a good linear relationship existed between the standard curve and the concentration of template. The lowest detection limit was 5.2 RNA molecules per reaction. This assay was specific for detection of BVDV-1, and no amplification was found for other pestiviruses such as classical swine fever virus (CSFV), border disease virus (BDV), and common infectious bovine viruses, including BVDV-2, infectious bovine rhinotracheitis virus (IBRV), bovine parainfluenza virus type 3 (BPIV-3), bovine respiratory syncytial virus (BRSV), bovine ephemeral fever virus (BEFV) and bovine coronavirus (BcoV). The assay was highly reproducible with low variation coefficient values (CVs) for intra-assay and inter-assay. A total of 169 aerosol samples collected from six dairy herds were tested using this method. The results showed that the positive detection rate of BVDV-1 was 17.2% (29/169), which was significantly higher compared with the conventional RT-PCR. Additionally, the positive samples (n = 29) detected by real-time RT-PCR were verified by BVDV RPA-LFD, and a concordance rate of 100% was obtained between them.ConclusionsTaken together, we developed a real-time RT-PCR assay for quantitative analysis of BVDV-1 in aerosol samples, and our finding provided valuable insights into the risk on aerosol transmission of BVDV-1.

Fabrication and mechanical properties of large‐scale SiC impeller via vacuum gelcasting and pressureless sintering

AbstractImpeller is the key part of centrifugal pump to convey liquid. And combined with the engineering practice, we fabricated two types of open and semi‐open SiC ceramic impellers with diameter of 100 mm and 160 mm via gelcasting and pressureless sintering. B4C and C were used as the sintering additives and sprayed drying granulation method was adopted for the starting SiC powder processing. Given the size and shape complexity of impeller, the optimized pH value, dispersant content, and solid‐loading content for the fabrication of the SiC impellers were determined to be 10‐11, 0.8 wt%, and 40 vol%, respectively. For the open impeller, blade height, cover board thickness, drying shrinkage, and sintering shrinkage are 10.5 mm, 4 mm, 10.3%, and 21.3%, respectively. For the semi‐open ones, the corresponding parameters are 41 mm, 10 mm, 10.3%, and 21.3%, respectively. The average density of the two types of impellers is 3.15 g/cm3, and the mechanical properties of both impellers, including average hardness, flexural strength, compressive strength, and fracture toughness are 2478 HV, 436 MPa, 2093 MPa, and 3.17 MPa·m1/2, respectively. All variation coefficient values are smaller than 5%, which indicates a good uniformity in densities and mechanical properties of both the impellers.

The impact of pins on dual-port microwave heating uniformity and efficiency with dual frequency

This work aims to improve the uniformity and efficiency of microwave heating. A dual-port simulation model based on the finite element method was built, and two pins were applied to the heating cavity. The impact of dual frequency and pins on the coefficient of variation (COV) and heating efficiency were investigated. The results demonstrated that the uniformity of dual-frequency heating can be improved by 15.4%. Moreover dual-frequency with double pins can maximally increase heating efficiency to 166.7% and the COV value can be reduced to 60.2%, compared with single-frequency heating. The heating effect of other materials was also analyzed. The uniform and efficient microwave heating were realized at dual frequency with pins.