Statistical Variability Research Articles

An integrated approach for parameter estimation of a propyl propionate synthesis model

This paper introduces an innovative approach to the ProPro synthesis process, aiming to improve the modeling and parameter estimation by integrating and optimizing existing methodologies. It combines well-established models available in the literature with a hybrid solution approach, emphasizing computational efficiency. Additionally, it assesses and enhance the modeling results by calculating confidence regions and uncertainties in both kinetic and thermodynamic modeling. To this end, a batch reactor with Amberlyst 46 catalyst is modeled. The parameter estimation approach combines Particles Swarm Optimization and Gradient Method to estimate both thermodynamic and kinetic parameters, sequentially and simultaneously. Confidence regions and uncertainties are determined for the sequential approach, guiding the search space for the simultaneous estimation. By utilizing PSO, the parameters are estimated, and their confidence regions are determined, providing a comprehensive understanding of their uncertainty. The uncertainty is propagated through the model predictions of the batch reactor, allowing for a comprehensive analysis of the system's behavior. The results demonstrate a good agreement between the model predictions and experimental data, with the expanded uncertainty adequately reflecting the statistical variability of the experimental observations. Furthermore, the heterogeneous Langmuir-Hinshelwood model yields improved representation of the experimental data in both transient and steady states compared to the pseudo-homogeneous model. The Root Mean Square Deviation (RMSD) for parameter estimation shows significant improvement compared to literature values. The simultaneous parameter estimation approach exhibits the best fit performance for the model predictions, confirming its effectiveness in accurately representing the system.

APPLICATION OF DIBR AND MAIRCA METHODS IN THE EVALUATION OF THE ECONOMIC PERFORMANCE OF THE ECONOMY OF BOSNIA AND HERZEGOVINA

The issue of analyzing factors of the dynamics of the economic performance of every economy, including Bosnia and Herzegovina (BiH), is continuously very current, challenging, significant, and complex. An adequate control of the key factors can significantly influence the achievement of the target economic performance of BiH’s economy. The application of multi-criteria decision-making methods enables an adequate control of the key factors of the economic performance of BiH’s economy. Bearing that in mind, this paper analyzes the dynamics of the economic performance of BiH’s economy in the period 2013 - 2022 based on the DIBR and MAIRCA methods. The top five years of the economic performance of BiH’s economy according to the DIBR and MAIRCA methods fall in the following order: 2021, 2022, 2018, 2019, and 2017. The worst economic performance in BiH’s economy was registered in 2020, which was contributed, among other things, by the Covid-19 pandemic. Generally speaking, the economic performance of BiH’s economy significantly improved recently. This was influenced by adequate management of the analyzed statistical variables (gross domestic product, inflation, agriculture, industry, export, import, capital, income, taxes, time required to start business – days, and domestic loans provided by the financial sector). The factors such as the geopolitical situation, the economic climate, foreign direct investments, the energy crisis, the digitalization of company's entire operation, the application of sustainable development concept and other others are also important. In any case, the adequate control of these variables can greatly influence the achievement of the target economic performance of BiH’s economy.

(Invited) Simulations of Ultra-Scaled Electronic Devices with a Novel Flexible Nano-TCAD Nano-Electronic Simulation Software (NESS) Environment

Simulation of conventional and emerging electronic devices using Technology Computer Aided Design (TCAD) tools has been an essential part of the semiconductor industry as well as academic research. Computational efficiency and accuracy of the numerical modeling are the key criteria on which quality and utility of a TCAD tool is ascertained. Further, the ability of the tool to incorporate different modeling paradigms and to be applicable to a wide range of device architectures and operating conditions is essential.In this talk, I will provide an overview of the new device simulator NESS (Nano-Electronic Software Simulator) developed at Device Modelling Group at University of Glasgow. NESS is a fast, modular software with its own structure and mesh generators, and contains different modules for classical, semi-classical, and quantum transport solvers, mobility calculation, kinetic Monte-Carlo etc. NESS can simulate numerous device architectures such as nanowire and bulk transistors, tunnelling field effect transistors (TFET) and resonant tunnelling diodes. Moreover, NESS accounts for various sources of statistical variability in nano-size electronic devices and it can perform statistical simulations for thousands microscopically different devices.

Assessing the use of digital soil maps in hydrological modeling for soil-water budget simulations - implications for water management plans in southern Portugal

Efficient water management plans are required to ensure food security in areas prone to drought and soil degradation. Hydrological modeling can help to achieve this goal by evaluating water availability for different uses, including food production. Fully distributed hydrological models using digital maps of soil properties available for the soil profile are useful for mapping soil-water balance responses, namely water content and water stress. The accuracy of these model responses depends on the quality of the input data, namely, soil hydraulic properties (SHP). Nowadays, we have free access to worldwide digital 1D SHP grids created using global soil datasets, so detailed studies are now needed to evaluate their use in hydrological modeling. We compared the use of a global and a local SHP dataset to simulate soil-water balance at the regional scale in a small irrigation district located in southern Portugal. We explicitly characterized where differences in model responses occur and related those to the variability of soil physical and hydraulic properties, and land use. Our results showed that the choice of the SHP dataset matters. The statistical and spatial variability of simulated water content and water stress for different land uses depended on the dataset used for the numerical simulation. With the global dataset, water content was higher and water stress lower, and both had less statistical and spatial variability compared to the local dataset results. A practical consequence of these findings is misadjusted irrigation schedules, which can be detrimental to crop production and soil quality. A water management plan based on the global results will determine less water requirements, which may not be realistic for the Mediterranean conditions that characterize the study area.

Synthesis of Solar Production and Energy Demand Profiles Using Markov Chains for Microgrid Design

Uncertainties related to the energy produced and consumed in smart grids, especially in microgrids, are among the major issues for both their design and optimal management. In that context, it is essential to have representative probabilistic scenarios of these environmental uncertainties. The intensive development and massive installation of smart meters will help to better characterize local energy consumption and production in the following years. However, models representing these variables over large timescales are essential for microgrid design. In this paper, we explore a simple method based on Markov chains capable of generating a large number of probabilistic production or consumption profiles from available historical measurements. We show that the developed approach can capture the main characteristics and statistical variability of real data on both short-term and long-term scales. Moreover, the correlation between both production and demand is conserved in generated profiles with respect to historical measurements.

Time-of-Flight Measurements in the Jet of a High-Current Vacuum Arc Thruster

Measurements of ion speed in the plume of a pulsed high-current vacuum arc thruster were performed by means of electrostatic probes. The probes were designed to provide direct speed measurements with minimum disturbance on the plasma jet. Typical mean values of vi for Ti and Cu cathodes are determined at different locations downstream of the electrodes, in the far field region. From one VAT discharge to another, the mean ion speed strongly varies which leads to a large statistical dispersion. Single-shot analysis allows the observation of the plume anisotropy and its high divergence as well as the existence of several ion groups of different speeds throughout a discharge.

Phase Angle and Body Composition As a Prognostic Factor in Acute Lymphoblastic Leukemia

Acute lymphoblastic leukaemia (ALL) is a malignant proliferation of lymphoid cells blocked at an early stage of differentiation that can invade bone marrow, blood, and extramedullary sites. Age specific incidence is highest in children aged 1-4 years, then drops sharply through childhood (5-14 years), adolescence and young adulthood (AYA) (15-39 years), reaching the lowest point between 25 years and 45 years. Bioelectrical impedance analysis (BIA) is a method used to estimate body composition and cell membrane integrity. BIA is a useful tool as it is non-invasive, relatively inexpensive, can be performed on nearly any patient, does not expose the patient to ionizing radiation, is painless, and has both high intra and inter observer precision (coefficient of variation = 2.7%-4.0%). Phase angle (PhA) is obtained by BIA and is associated with cellular function. It is considered a reliable marker of malnutrition. PhA has been shown to predict survival in solid malignancies and hematopoietic stem cell transplant patients. To date, no studies have evaluated the usage of PhA in ALL patients. Therefore, this retrospective study sought to establish the prognostic significance of baseline PhA and lean mass index on OS and LFS in newly diagnosed ALL patients receiving intensive chemotherapy. Retrospective, cross-section, observational and descriptive study. The records of patients who received intensive chemotherapy from January 2019 to January 2023 were reviewed. Statistical analysis The qualitative variables were studied in frequencies and proportions, the quantitative variables were grouped into medians and ranges. OS and LFS were determined using Kaplan-Meier survival curves with log-Rank with a significant p <0.05 value. Statistical analysis was performed with SPSS version 25 and GraphPad Prism version 9.5.0. Results 85 patients were included, 56.7% (48) men and 43.5% (37) women. 79 patients with ALL-B and 6 patients ALL-T. The mean age was 25 years. 68 were AYA population and 17 not-AYA. The CR was 89%, ND MRD was 57%. The chemotherapy for AYA was CALGB 10403, and not AYA was Hyper-CVAD. Relapse was documented in 38%. The mean body mass index was 26.98±5.27 kg/m 2. The mean PhA was 4.547±0.9983°. The mean lean mass index was 17.8 (12.9-35.5) kg/m 2. The mean fat mass index was 9.195±4.425 kg/m 2. The mean OS was 86% at 1 year and OS at 3 years was 64.5%. The results that were statistically significant in LFS compared by Kaplan Meier curves were: male vs female p=0.0344, PhA >4, p=0.0235, lean mass index ≥16, p=0.0111. Conclusions In conclusion, our findings suggest that in newly diagnosed ALL patients undergoing intensive induction chemotherapy, PhA may provide important prognostic information for LFS and OS. PhA is an objective, repeatable, high-precision measure in ALL patients and, unlike other prognostic factors in this population, is potentially subject to intervention. Future studies of PhA in ALL patients should address the content validity of phase angle while further exploring the promising findings of the effect of strength training and nutritional supplementation on PhA and patient outcomes.

Influence of Sorghum bicolor (L.) Moench. seeds treatment with biological preparations on its sowing qualities

The article presents the results of studies on the effect of sorghum bicolor seeds (Sorghum bicolor (L.)) Moench treatment with a mixture of the mycorrhizal biopreparation «Mycofriend» and the biologically active adsorbent «BM-nanobiochar» on germination energy and laboratory seed germination. The optimal doses of biological preparations «Mikofrend» and «BM-nanobiochar», which ensure the maximum sowing quality of seeds, have been established. The aim of the study is to establish the optimal dose of biochar and mycorrhizal biopreparation, which ensures the highest sowing quality of sorghum bicolor seeds. The subject of the research is sowing qualities of sorghum bicolor seeds, mycorrhizal biopreparation and biochar. The research methods were biological (conducting a laboratory experiment) and statistical (descriptive statistics, dispersion, correlation and regression analyses) ones. The research results showed that the use of «Micofrend» for the treatment of sorghum bicolor seeds at a dose of 3–6 g/kg increases the energy of seed germination to 88.63–88.00 % (control – 84.81 %) and laboratory germination to 90.69 % (control – 86.69 %). The use of biological preparation «BM-nanobiochar» at a dose of 3–6 g/kg provided an increased energy of seed germination to 88.75–87.81 % (control – 86.31 %) and laboratory germination to 90.44–90.63 % (control – 88.94 %). Increasing the dose of both tested biological preparations to 9 g/kg led to a deterioration of the sowing qualities of the seeds. In the experiment the highest germination energy (92.25 %) and laboratory germination (93.5 %) was observed when treating sorghum bicolor seeds with a mixture of «Micofrend» and «BM-nanobiochar» at a dose of 6 and 3 g/kg respectively. The lowest rate of germination energy (81.75 %) was observed in the control variant without seed treatment with biological preparations. A close curvilinear relationship (R2 =0.81–0.98) was established between the sowing qualities of sorghum bicolor seeds and the doses of biological preparations «Mycofriend» and «BM-nanobiochar». The presence of a close multiple correlation between the sowing quality of the seed and its treatment with biological preparations «Micofrend» and «BM-nanobiochar» (R=0.867) was proved. Key words: germination energy, laboratory germination, mycorrhizal preparation, biochar, sustainable development, climate agreement, green European course, bioenergy.

Application of AC superimposed DC waveforms to bismuth electrorefining

Electrorefining in molten salts is used for purifying actinides. Optimizing electrorefining is key to minimizing processing time and radiological waste. One possible way of improving electrorefining efficiency is using an AC superimposed DC waveform. This waveform has demonstrated potential benefits in aqueous solutions but has never been utilized in a molten metal, molten salt application. This work investigates the effects of using an AC superimposed DC waveform on molten bismuth electrorefining in a molten LiCl–KCl–CaCl2 eutectic. Bismuth has been identified as a potential surrogate for plutonium electrorefining and a potential cathode in electrorefining used nuclear fuel (UNF). All electrorefining runs resulted in a high purity cathode ring and high yield with exception of the run using a low-frequency, high-amplitude superimposed AC waveform, which experienced some contamination and a lower yield. The other three AC superimposed DC runs experienced an average yield 6.7 % higher than the average yield of the DC runs. The electrorefining run using the high-frequency, high-amplitude superimposed AC signal had the highest yield. It is recommended in future studies to investigate the statistical variability of electrorefining yield and current efficiency and the impact of AC superimposed DC waveforms on solidified bismuth anodes.

Reappraisal of clinical trauma trials: the critical impact of anthropometric parameters on fracture gap micro-mechanics—observations from a simulation-based study

The evidence base of surgical fracture care is extremely sparse with only few sound RCTs available. It is hypothesized that anthropometric factors relevantly influence mechanical conditions in the fracture gap, thereby interfering with the mechanoinduction of fracture healing. Development of a finite element model of a tibia fracture, which is the basis of an in silico population (n = 300) by systematic variation of anthropometric parameters. Simulations of the stance phase and correlation between anthropometric parameters and the mechanical stimulus in the fracture gap. Analysis of the influence of anthropometric parameters on statistical dispersion between in silico trial cohorts with respect to the probability to generate two, with respect to anthropometric parameters statistically different trial cohorts, given the same power assumptions. The mechanical impact in the fracture gap correlates with anthropometric parameters; confirming the hypothesis that anthropometric factors are a relevant entity. On a cohort level simulation of a fracture trial showed that given an adequate power the principle of randomization successfully levels out the impact of anthropometric factors. From a clinical perspective these group sizes are difficult to achieve, especially when considering that the trials takes advantage of a „laboratory approach “, i.e. the fracture type has not been varied, such that in real world trials the cohort size have to be even larger to level out the different configurations of fractures gaps. Anthropometric parameters have a significant impact on the fracture gap mechanics. The cohort sizes necessary to level out this effect are difficult or unrealistic to achieve in RCTs, which is the reason for sparse evidence in orthotrauma. New approaches to clinical trials taking advantage of modelling and simulation techniques need to be developed and explored.

Intestinal and Renal Adaptations to Changes of Dietary Phosphate Concentrations in Rat.

We have studied the role of the intestine, kidney, and several hormones when adapting to changes in dietary P concentration. Normal and parathyroidectomized (PTX) rats were fed pH-matched diets containing 0.1%, 0.6%, and 1.2% P concentrations. 32Pi uptake was determined in the jejunum and kidney cortex brush border membrane vesicles. Several hormone and ion concentrations were determined in the blood and urine of rats. Both jejunum and kidney cortex Pi transport was regulated with 5 d of chronic feeding of P diets in normal rats. Acute adaptation was determined by switching foods on day 6, which was only clearly observed in the kidney cortex of normal rats, with more statistical variability in the jejunum. However, no paradoxical increase of Pi uptake in the jejunum was reproduced after the acute switch to the 1.2% P diet. Pi uptake in the jejunum was parathyroid hormone (PTH)-independent, but in the kidney, the chronic adaptation was reduced, and no acute dietary adaptations were observed. The NaPi2a protein was more abundant in the PTX than the sham kidneys, but contrary to the modest or absent changes in Pi uptake adaptation, the transporter was similarly regulated by dietary P, as in the sham rats. PTH and fibroblast growth factor 23 (FGF23) were the only hormones regulated by all diet changes, even in fasting animals, which exhibited regulated Pi transport despite similar phosphatemia. Evidence of Pi appetite effects was also observed. In brief, our results show new characteristics of Pi adaptations, including a lack of correlation between Pi transport, NaPi2a expression, and PTH/FGF23 concentrations.

Accounting for the Concreteness and Neighborhood Effects in a High Frequency Word List for Poor Readers

Some poor readers show little or no progress in literacy interventions as their susceptibility to the concreteness and neighborhood effect is not accounted for during intervention. This study aims to develop a resource for poor readers by revising the Dolch list to account for the concreteness and neighborhood (orthographic, phonological and semantic) effect. Psycholinguistic techniques were employed to recategorize 220 Dolch list words according to concreteness via function and content word categories, and include the associated orthographic, phonological and semantic neighbors of each word into a new High Frequency List with Neighbors (HFLN). One-way analysis of variance (ANOVA), Bonferroni post hoc test and Levene’s test of variance homogeneity were carried out as measures of statistical significance and variability. The HFLN contains a total of 220 words with 1057 neighbors across five function and content word categories. Both measures of statistical significance and variability show that grade categories in the Dolch list contain greater mean concreteness values with overlapping similarities and higher variability. Conversely, the HFLN effectively delineates concreteness value clusters between categories with lower variability. The HFLN aids in targeted intervention of poor readers by presenting the available orthographic, phonological and semantic neighbors according to the descending order of concreteness.

Not Only Length Matters! Impact of the Ileal Width on the Capacity of the Orthotopic Neobladder: The AADAPT Formula Tested on the Animal Model

BackgroundThe capacity of a given shape of an orthotopic ileal neobladder (ONB) varies significantly, although the same length of preterminal ileum is utilised. ObjectiveTo investigate the variability of the human ileal width and to create a mathematical formula that calculates its impact on the neobladder capacity. Design, setting, and participantsDuring 50 consecutive cases of robotic pelvic surgery, a segment of preterminal ileum was identified and the width was measured. A mathematical formula was created to calculate, for a given ileal length and width, the neobladder capacity and, for a given ileal width and neobladder capacity, the length of the (pre)terminal ileum to harvest. The accuracy of our model was tested on 28 pouches created by swine ileum. Outcome measurements and statistical analysisThe interindividual variability of the ileal width and its impact on the ileal neobladder capacity was investigated. Results and limitationsThe mean hemicircumference of the human distal ileum is 2.43 ± 0.39 cm (range 2–3.5 cm). According to our geometric model and as confirmed in the swine model, an increase of 1 cm in ileal width increases the neobladder capacity by 85%. The Pearson correlation coefficient reported a strong positive relationship between the formula-calculated and effective volumes of the pouch (r = 0.97). Moreover, for the same target capacity, 1 cm of difference in the ileal width implies harvesting 20 cm less ileum. A lack of testing on humans and application only to spheroidal neobladders are the main limits. ConclusionsThe ileal width impacts the capacity of the ONB. For a given type of ONB, no standard length of ileum should be harvested; instead, the length should be tailored to the width of the ileum for a given patient. Clinical studies are required to confirm our model. Patient summaryWe demonstrated the variability of the ileal width among humans, and we provided a mathematical formula tested on swine that evaluates the impact of the ileal width on the capacity of the orthotopic ileal neobladder.

REMOTE SENSING AND IN-SITU-BASED ASSESSMENT OF GREENHOUSE GASES IN NIGERIA

In data-sparse locations, the necessity for the integration of remote sensing and in-situ-based approaches in assessing greenhouse gases cannot be overstressed. Akin other countries in sub-Saharan Africa (SSA), Nigeria is yet to leverage on and fully maximize the potentialities offered by satellite remote sensing in monitoring and assessment of biophysical and ecological change indicators including greenhouse gases. This study was undertaken with the prime motivation of ascertaining the variations of greenhouse gases concentrations in Delta State, Nigeria as well as the correlation between in-situ measurement and satellite remote sensing observation. Datasets comprising carbon monoxide (CO), nitrogen dioxide (NO2) and sulfur dioxide (SO2) and were sourced from the archive of the European Space Agency and field sampling using Aeroqual S500 ambient air analyser. Descriptive statistics, independent Samples t-Test, analysis of variance (ANOVA), Tukey HSD test of multiple comparisons and simple linear regression (SLR) were the major inferential statistical frameworks used in the study. The results showed that greenhouse gases exhibited statistical significant spatial variability with the non-fictional variation of CO from In-situ measurement domiciled between Delta South Senatorial District (SD) and Delta North SD with Mean Difference of – 0.05 (p-value of 0.027 < 0.05). Validity, extent of accuracy and reliability of remotely-sensed greenhouse gases with in-situ observations was also established with CO, SO2 and NO2 in Delta South SD being statistically significant at 95% confidence level. The paper recommends the adoption of space-borne satellite remote sensing resources and GIS in periodic monitoring, mapping and assessments of environmental change indicators.

Hybrid experimental designs for joint estimation of absolute and relative retention curves for trawl gears

Abstract Methods for jointly estimating both the size-specific relative retention and absolute retention (retention probability) of two experimental trawl gears are considered. One approach would be to undertake comparative fishing of both gears, from which their comparative catchability can be estimated directly. If comparative catchability can be corrected for differing sampling effort and fishing efficiency of the two gears, then relative retention can be estimated. Furthermore, if a suitable functional form of the absolute retention curve is assumed, then estimates of absolute retention can potentially be obtained. However, these estimated retention curves are seen to have extremely large statistical variability and will not be useful in practice. On the other hand, if the gears are each fished with a non-selective control, then absolute retention can be directly estimated, from which estimates of relative retention can immediately be obtained. However, these estimates of relative retention have greater variability than would be obtained by comparative fishing with the same level of sampling effort. It is shown that a hybrid selectivity design that includes both comparative fishing of the experimental trawls and fishing with a non-selective control provides a more balanced approach. An extensive simulation study is conducted using scenarios based on recently published work on selectivity experiments targeting cod (Gadus Morhua) and hoki/blue grenadier (Macruronus novaezelandiae).

Reevaluating Contour Visualizations for Power Systems Data

Effective visual analytics tools are needed now more than ever as emerging energy systems data and models are rapidly growing in scale and complexity. We examined the suitability of colored contour maps to visually represent bus values in two different power system models: a dense 24k-bus distribution system and a 240-bus transmission system. In a quantitative analysis, we found that contour maps misrepresent power systems data, changing the statistical dispersion of the bus values, including the loss of extreme values. In a controlled empirical study with thirty professional power system research engineers, we found that these distortions significantly impact excursion identification tasks. Additionally, the engineers were less confident in their assessments using contour-based visualizations than glyph-based visualizations.

Evaluating the Perception for Psychological and Social Impact of Infertility among Libyans

Background: The infertility is defined as inability to conceive after one year of regular unprotected sexual intercourse which classified into primary or secondary infertility. Several studies had proven the adverse impacts of psychological and social aspects on infertile couples and the reported prevalence of psychological problems were estimated between 25 to 60%. Thence, emerging the psychological interventions among infertile couples are positively correlated with fewer psychological distress, higher rates of pregnancy and improving marital satisfaction. Objective: To evaluate the perception for psychological and social impact of infertility among Libyans. Methods and Materials: This study was cross-sectional which conducted during July 2022 by using an electronic questionnaire survey. 154 participants had responded during the study period and the collected data had entered, encoded and analyzed by using SPSS version 20 to illustrated the descriptive statistics variables. Results: We studied 154 Libyan participants which respond to electronic survey during July 2022.Majority of participants were females with predominance percentage 92.9% (143) while just 7.1% (11) were males.The most frequent age range were between 34 to 41 years which accounts 35.7% (55) followed by 28.6% (44) for age range between 26 to 33 years. Most of responders had university educational level which scored 77.9% (120). Regarding the marital status, majority of them were married which accounts 81.8% (126) while 16.2% (25) were single and only three (1.9%) were divorced. Among the married group (126 participants) and divorced group (three participants), 72.1% (93) of them had expressed history of infertility issues and delayed childbearing which almost of them reported to had suffered from psychosocial problems. On assess the perception of participants regarding the effect of the psychological factor on patients with infertility and delayed childbearing, the minimum percentage was 71.4% while the maximum percentage was 93.5% which considered to be high perception level. While on determine the perception of participants regarding the impact of the social factor on patients with infertility and delayed childbearing, the minimum percentage was 56.6% while the maximum percentage was 93.5%. On demonstrate the perception of participants regarding the effect of warfare remnants on infertility, 90.3% had perception to negative effect of warfare to women mental health and 89.6% had perception to negative effect of warfare to men mental health. And both considered to be high perception level. Lastly, on evaluate the perception of participants regarding the psychological effect of Corona pandemic which contributed to delayed childbearing and infertility, 74.7% (115) had expressed relatively to consider high perception. Conclusion: The perception of the participants regarding the impact of the psychological and social factors on infertility and delayed childbearing was considered to be high with positive results reported. Therefore, maintaining the health education approach is basic and essential pillars for raising health awareness particularly among infertile couples along with providing psychological and social support for that group during the treatment journey are important to accomplish favorable management outcomes.

The Design and Process Reliability Analysis of Millimeter Wave CMOS Power Amplifier with a Cold Mode MOSFET Linearization

A power amplifier design operating at 28 GHz for communication applications is presented in this paper. Analog predistorted technique is used to improve the linearity using a cold mode MOSFET linearizer. The paper reports +19.8 dBm of peak power at the output and power-added efficiency (PAE) of 17% is attained by the designed circuit. The 1-dB compression point linearity was +18.6 dBm. The adjacent channel power ratio (ACPR) simulations were performed for the different communication standards like 802_11n_40M, CDMA, IS-95, and 802_11n_20M. Design specification variations of the amplifier have been analyzed over five process corners and simulations were performed to validate compliance with standards and robustness of the designed circuit. Monte Carlo simulation were performed to assess the performance over statistical variability of PAE and power gain. It is believed that this linearization design and the verifications used are done for the first time on a 65-nm RFCMOS process.

Influence of Performance Appraisal on Employee Performance in the Energy Sector Kenya

Abstract
 The study focused more on exploring performance appraisal regarding employee performance to ascertain the influence of performance evaluation on employee performance in the energy sector. Similarly the objective of this research was to look into the result of goal setting on employee performance, to find out how career plans influence on workers’ effectiveness, and for determining the extent to which competency-based evaluation influence employees performance, to investigate the impact of ongoing feedback through employee achievement and to assess how incentives affect employee performance in Kenya energy sector through a research paper survey of Kenya Power Ltd. (KP), Kenya Electricity Transmission Company Ltd. (KETRACO), and Kenya Electricity Generating Company PLC. (KenGen), all of which are located in Nairobi County. The researcher used explanatory sequential design method. The study's population was 8820 employees, 11% of total population utilizing a sample size of 801 participant attracted as for all divisions in and to organizations, varying from Senior, middle, and lower-level management employees. Consequently, the researcher used a random sampling technique to collect data from respondents at various levels of management in Kenya's energy sector. Semi-structured questionnaires were used to gather primary data because they allow for open-ended responses from respondents and allow the researcher to easily prepare questions ahead of time to guide the discussion and keep the participants on topic. The collected data was analyzed by use of descriptive statistics and the Statistical Package for Social Sciences (SPSS). Finally, the data was interpreted into measures of central tendency, statistical dispersion, percentages, and person correlations utilizing the frequency distribution. Results were shown in tables, bar charts, and graphs will be used for information presentations. In relation to the impact on employee performance of performance appraisal, the observations suggest that the assessment leads to enhanced productivity in an organization. An effective evaluation model can increase the employees' interest and performance to achieve the specific objectives of the organization. Regarding the influence performance feedback on employee service delivery, the findings showed that effective feedback is crucial to employees to achieve their set objectives. Feedback allows employees to know exactly what is expected of them. The key to the successful empowerment and productivity is effective performance feedback between employees and supervisors. Adequate feedback builds accountability, as staff and supervisors contribute to development goals, skills identification, career development and motivation of employees for enhanced performance. The study concluded that efficient performance appraisal practices allow employees to express their performance challenges, ideas in achieving individual and company's set objectives. Effective feedback on measuring performance can result in improved productivity of employees. In order to improve employee performance, the study recommends optimizing practices for performance management. The contribution of each employee to accomplishing company goals should be the main emphasis of performance reviews.

Comparison of prediction methods for added power and propeller revolution for a 1,800 TEU container ship using resistance tests in regular and irregular waves

This paper predicts the added power and propeller revolution due to irregular head waves for a 1,800 TEU container ship. Resistance tests were conducted with 11 regular waves and irregular waves at SS = 5. Time series (TS) and autocovariance analysis methods were applied to estimate statistical variables and uncertainties. The paper investigated the statistical convergence times of measured data. The wave elevation, heave and pitch motions obtained from the TS agree well with those from spectral analysis in regular and irregular waves. The added resistance from the TS is larger than that from spectral analysis using a regular wave test by 6.1%. The characteristics of response operators and spectra of the added (or reduced) propulsion performances and overload factors are discussed. The power and propeller revolution were evaluated with a variety of methods: SA(LVM-W), LVM-IR, DPM, and RTIM.