Inaccuracy in arc power calculation through a product of voltage and current averages

AbstractPower is an indirect measurand, determined by processing voltage and current analogue signals through calculations. Using arc welding as a case study, the objective of this work was to bring up subsidies for power calculation. Based on the definitions of correlation and covariance in statistics, a mathematical demonstration was developed to point out the difference between the product of two averages (e.g. P = $$\overline{U} x \overline{I}$$ U ¯ x I ¯ ) and the average of the products (e.g. P = ($$\overline{UxI}$$ UxI ¯ ). Complementarily, a brief on U and I waveform distortion sources were discussed, emphasising the difference between signal standard deviations and measurement errors. It was demonstrated that the product of two averages is not the same as the average of the products, unless in specific conditions (when the variables are fully correlated). It was concluded that the statistical correlation can easily flag the interrelation, but if assisted by covariance, these statistics quantify the inaccuracy between approaches. Finally, although the statistics' determination is easy to implement, it is proposed that power should always be calculated as the average of the instantaneous U and I products. It is also proposed that measurement error sources should be observed and mitigated, since they predictably interfere in power calculation accuracy.

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Effect of Implantable Collamer Lens on Anterior Segment Measurement and Intraocular Lens Power Calculation Based on IOLMaster 700 and Sirius

Journal of Ophthalmology ◽

10.1155/2021/8988479 ◽

2021 ◽

Vol 2021 ◽

pp. 1-7

Author(s):

Xiaoyong Chen ◽

Di Zhang ◽

Ziyuan Liu ◽

Yinan Liu ◽

Hongyuan Cai ◽

...

Keyword(s):

Ray Tracing ◽

Intraocular Lens ◽

Measurement Errors ◽

Corneal Thickness ◽

Power Calculation ◽

Anterior Surface ◽

Implantable Collamer Lens ◽

Iol Power ◽

The Difference ◽

Iolmaster 700

Purpose. To investigate the possible effect of an implantable collamer lens (ICL) on ocular biometrics and intraocular lens (IOL) power calculation. Methods. Ocular measurements were taken preoperatively and at the two-month follow-up using IOLMaster 700 and Sirius in 85 eyes (43 patients) who had previously undergone ICL surgery. IOL power was calculated using either IOLMaster 700 (Barrett Universal II formula) or Sirius (ray-tracing). All data were compared using the paired t-test. Results. The difference between preoperative and postoperative anterior chamber depth (ACD), lens thickness (LT), and keratometry on the steep axis (K2) measured by IOLMaster 700 was statistically significant (p < 0.001). In 11 of 85 eyes, IOLMaster misjudged the anterior surface of the ICL as that of the lens, leading to an error in ACD and LT. There were no significant differences between preoperative and postoperative axial length (AL) (p = 0.223), white to white (WTW) (p = 0.100), keratometry on flat axis (K1) (p = 0.117), or central corneal thickness (CCT) (p = 0.648), measured using IOLMaster. The difference in IOL power calculated using the Barrett II formula was significant (p = 0.013). Regression analysis showed that AL and K had the greatest influence on IOL calculation (p < 0.001), and ACD and LT had less influence (p = 0.002, p = 0.218, respectively). K1 and K2 were modified to exclude the influence of K2, and modified IOLs showed no difference between pre and postoperation (p = 0.372). Preoperative and postoperative ACD measured using Sirius were significantly different (p < 0.001); however, the IOL power calculated using ray-tracing technology showed no significant differences (p > 0.05). Conclusions. The ocular biometric apparatus may misjudge the anterior surface of the lens, resulting in measurement errors of ACD and LT, which has little effect on the calculation of IOL power when using IOLMaster 700 (Barrett Universal II formula) and Sirius (ray-tracing).

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EVALUASI PROYEKSI DEMAND BARANG DAN PENUMPANG PELABUHAN DI PROVINSI MALUKU

Jurnal Transportasi ◽

10.26593/jt.v19i2.3467.101-110 ◽

2019 ◽

Vol 19 (2) ◽

pp. 101-110

Author(s):

Adrian Firdaus ◽

M. Dwi Yoga Sutanto ◽

Rajin Sihombing ◽

M. Weldy Hermawan

Keyword(s):

Time Series ◽

Projection Method ◽

Development Plan ◽

Master Plan ◽

Port Development ◽

Loading And Unloading ◽

The Difference ◽

Existing Data

Abstract Every port in Indonesia must have a Port Master Plan that contains an integrated port development plan. This study discusses one important aspect in the preparation of the Port Master Plan, namely the projected movement of goods and passengers, which can be used as a reference in determining the need for facilities at each stage of port development. The case study was conducted at a port located in a district in Maluku Province and aims to evaluate the analysis of projected demand for goods and passengers occurring at the port. The projection method used is time series and econometric projection. The projection results are then compared with the existing data in 2018. The results of this study show that the econometric projection gives adequate results in predicting loading and unloading activities as well as the number of passenger arrival and departure in 2018. This is indicated by the difference in the percentage of projection results towards the existing data, which is smaller than 10%. Whereas for loading and unloading activities, time series projections with logarithmic trends give better results than econometric projections. Keywords: port, port master plan, port development, unloading activities Abstrak Setiap pelabuhan di Indonesia harus memiliki sebuah Rencana Induk Pelabuhan yang memuat rencana pengem-bangan pelabuhan secara terpadu. Studi ini membahas salah satu aspek penting dalam penyusunan Rencana Induk Pelabuhan, yaitu proyeksi pergerakan barang dan penumpang, yang dapat dipakai sebagai acuan dalam penentuan kebutuhan fasilitas di setiap tahap pengembangan pelabuhan. Studi kasus dilakukan pada sebuah pelabuhan yang terletak di sebuah kabupaten di Provinsi Maluku dan bertujuan untuk melakukan evaluasi ter-hadap analisis proyeksi demand barang dan penumpang yang terjadi di pelabuhan tersebut. Metode proyeksi yang dipakai adalah proyeksi deret waktu dan ekonometrik. Hasil proyeksi selanjutnya dibandingkan dengan data eksisting tahun 2018. Hasil studi ini menunjukkan bahwa proyeksi ekonometrik memberikan hasil yang cukup baik dalam memprediksi aktivitas bongkar barang serta jumlah penumpang naik dan turun di tahun 2018. Hal ini diindikasikan dengan selisih persentase hasil proyeksi terhadap data eksisting yang lebih kecil dari 10%. Sedangkan untuk aktivitas muat barang, proyeksi deret waktu dengan tren logaritmik memberikan hasil yang lebih baik daripada proyeksi ekonometrik. Kata-kata kunci: pelabuhan, rencana induk pelabuhan, pengembangan pelauhan, aktivitas bongkar barang

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Analysis of the System of Controlling Paid Parking Zones

Sustainability ◽

10.3390/su13084211 ◽

2021 ◽

Vol 13 (8) ◽

pp. 4211

Author(s):

Maciej Kozłowski ◽

Andrzej Czerepicki ◽

Piotr Jaskowski ◽

Kamil Aniszewski

Keyword(s):

Control System ◽

Smart City ◽

Measurement Errors ◽

Fundamental Problem ◽

Urban Traffic ◽

Statistical Dependence ◽

Actual State ◽

Event Time ◽

Operational Data

Urban traffic can be curbed in various ways, for instance, by introducing paid unguarded parking zones (PUPZ). The operational functionality of this system depends on whether or not the various system features used to document parking cases function properly, including those which enable positioning of vehicles parked in the PUPZ, recognition of plate numbers, event time recording, and the correct anonymisation of persons and other vehicles. The most fundamental problem of this system is its reliability, understood as the conformity of control results with the actual state of matters. This characteristic can be studied empirically, and this article addresses the methodology proposed for such an examination, discussed against a case study. The authors have analysed the statistical dependence of the e-control system’s measurement errors based on operational data. The results of this analysis confirm the rationale behind the deployment of the e-control system under the implementation of the smart city concept in Warsaw.

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Using a Process Approach to Pandemic Planning: A Case Study

Applied Sciences ◽

10.3390/app11094121 ◽

2021 ◽

Vol 11 (9) ◽

pp. 4121

Author(s):

Hana Tomaskova ◽

Erfan Babaee Tirkolaee

Keyword(s):

Process Model ◽

Process Mining ◽

Process Approach ◽

Research Topic ◽

Future Research ◽

Critical Situation ◽

Pandemic Planning ◽

The Difference ◽

Smart Technologies

The purpose of this article was to demonstrate the difference between a pandemic plan’s textual prescription and its effective processing using graphical notation. Before creating a case study of the Business Process Model and Notation (BPMN) of the Czech Republic’s pandemic plan, we conducted a systematic review of the process approach in pandemic planning and a document analysis of relevant public documents. The authors emphasized the opacity of hundreds of pages of text records in an explanatory case study and demonstrated the effectiveness of the process approach in reengineering and improving the response to such a critical situation. A potential extension to the automation and involvement of SMART technologies or process optimization through process mining techniques is presented as a future research topic.

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THE VALUE OF ROBUST STATISTICAL FORECASTS IN THE COVID-19 PANDEMIC

National Institute Economic Review ◽

10.1017/nie.2021.9 ◽

2021 ◽

Vol 256 ◽

pp. 19-43

Author(s):

Jennifer L. Castle ◽

Jurgen A. Doornik ◽

David F. Hendry

Keyword(s):

Structural Change ◽

Measurement Errors ◽

Epidemiological Models ◽

Short Term ◽

Data Measurement ◽

Policy Interventions ◽

Changing Trends ◽

Technological Advances ◽

The Difference ◽

The Uk

The Covid-19 pandemic has put forecasting under the spotlight, pitting epidemiological models against extrapolative time-series devices. We have been producing real-time short-term forecasts of confirmed cases and deaths using robust statistical models since 20 March 2020. The forecasts are adaptive to abrupt structural change, a major feature of the pandemic data due to data measurement errors, definitional and testing changes, policy interventions, technological advances and rapidly changing trends. The pandemic has also led to abrupt structural change in macroeconomic outcomes. Using the same methods, we forecast aggregate UK unemployment over the pandemic. The forecasts rapidly adapt to the employment policies implemented when the UK entered the first lockdown. The difference between our statistical and theory based forecasts provides a measure of the effect of furlough policies on stabilising unemployment, establishing useful scenarios had furlough policies not been implemented.

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E-learning-Oriented Software Architecture Design and Case Study

International Journal of Emerging Technologies in Learning (iJET) ◽

10.3991/ijet.v10i4.4698 ◽

2015 ◽

Vol 10 (4) ◽

pp. 59

Author(s):

Peng Lu ◽

Xiao Cong ◽

Dongdai Zhou

Keyword(s):

Software Architecture ◽

Building Blocks ◽

Domain Model ◽

Learning System ◽

Application Framework ◽

Component Library ◽

E Learning ◽

The Difference ◽

High Level

Nowadays, E-learning system has been widely applied to practical teaching. It was favored by people for its characterized course arrangement and flexible learning schedule. However, the system does have some problems in the process of application such as the functions of single software are not diversified enough to satisfy the requirements in teaching completely. In order to cater more applications in the teaching process, it is necessary to integrate functions from different systems. But the difference in developing techniques and the inflexibility in design makes it difficult to implement. The major reason of these problems is the lack of fine software architecture. In this article, we build domain model and component model of E-learning system and components integration method on the basis of WebService. And we proposed an abstract framework of E-learning which could express the semantic relationship among components and realize high level reusable on the basis of informationized teaching mode. On this foundation, we form an E-learning oriented layering software architecture contain component library layer, application framework layer and application layer. Moreover, the system contains layer division multiplexing and was not built upon developing language and tools. Under the help of the software architecture, we could build characterized E-learning system flexibly like building blocks through framework selection, component assembling and replacement. In addition, we exemplify how to build concrete E-learning system on the basis of this software architecture.

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Magnetotelluric static shift: Estimation and removal using the cokriging method

Geophysics ◽

10.1190/1.2400625 ◽

2007 ◽

Vol 72 (1) ◽

pp. F25-F34 ◽

Cited By ~ 11

Author(s):

Benoit Tournerie ◽

Michel Chouteau ◽

Denis Marcotte

Keyword(s):

Apparent Resistivity ◽

A Priori ◽

Shift Factor ◽

Static Shift ◽

Geostatistical Model ◽

Data Set ◽

Resistivity Sounding ◽

The Difference ◽

Cross Variogram

We present and test a new method to correct for the static shift affecting magnetotelluric (MT) apparent resistivity sounding curves. We use geostatistical analysis of apparent resistivity and phase data for selected periods. For each period, we first estimate and model the experimental variograms and cross variogram between phase and apparent resistivity. We then use the geostatistical model to estimate, by cokriging, the corrected apparent resistivities using the measured phases and apparent resistivities. The static shift factor is obtained as the difference between the logarithm of the corrected and measured apparent resistivities. We retain as final static shift estimates the ones for the period displaying the best correlation with the estimates at all periods. We present a 3D synthetic case study showing that the static shift is retrieved quite precisely when the static shift factors are uniformly distributed around zero. If the static shift distribution has a nonzero mean, we obtained best results when an apparent resistivity data subset can be identified a priori as unaffected by static shift and cokriging is done using only this subset. The method has been successfully tested on the synthetic COPROD-2S2 2D MT data set and on a 3D-survey data set from Las Cañadas Caldera (Tenerife, Canary Islands) severely affected by static shift.

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Total Pressure Correction of a Sub-Miniature Five-Hole Probe in Areas of Pressure Gradients

Volume 1: Aircraft Engine; Ceramics; Coal, Biomass and Alternative Fuels; Controls, Diagnostics and Instrumentation ◽

10.1115/gt2012-69280 ◽

2012 ◽

Author(s):

J. Town ◽

A. Akturk ◽

C. Camcı

Keyword(s):

Pressure Measurement ◽

Measurement Errors ◽

Total Pressure ◽

Pressure Gradients ◽

Pressure Data ◽

Flow Conditions ◽

Complex Flow ◽

Ducted Fan ◽

The Difference ◽

Best Fit

Five-hole probes, being a dependable and accurate aerodynamic tools, are excellent choices for measuring complex flow fields. However, total pressure gradients can induce measurement errors. The combined effect of the different flow conditions on the ports causes the measured total pressure to be prone to a greater error. This paper proposes a way to correct the total pressure measurement. The correction is based on the difference between the measured total pressure data of a Kiel probe and a sub-miniature prism-type five-hole probe. By comparing them in a ducted fan related flow field, a line of best fit was constructed. The line of best fit is dependent on the slope of the line in a total pressure versus span and difference in total pressure between the probes at the same location. A computer program, performs the comparison and creates the correction equation. The equation is subsequently applied to the five-hole probe total pressure measurement, and the other dependent values are adjusted. The validity of the correction is then tested by placing the Kiel probe and the five-hole probe in ducted fans with a variety of different tip clearances.

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Forest biomass and wood consumption In the lower course of the Amazon: a case study of rhe Urubueua Island

Acta Amazonica ◽

10.1590/1809-43921999291095 ◽

1999 ◽

Vol 29 (1) ◽

pp. 79-79 ◽

Cited By ~ 3

Author(s):

Akio TSUCHIYA ◽

Mario HIRAOKA

Keyword(s):

Water Stress ◽

Forest Structure ◽

Forest Biomass ◽

Human Intervention ◽

Terra Firme ◽

Wood Volume ◽

The Difference ◽

Várzea Forests ◽

Wood Consumption

Várzea and terra-firme forests in the lower course of the Amazon were compared in terms of forest structure, wood volume increments and forest biomass. The wood volume of várzea forests was smaller than that of terra-firme forests, particularly when severe human intervention such as the cultivation of açaí palm occurred. The difference was even greater in the forest weight comparison because of the lower wood density of várzea trees. These trees are not directly influenced by water stress during the dry season, while late wood with a high density is formed in the terra-firme trees. The annual forest disappearance area due to firewood for tile factories was estimated to be about 276 ha on the island investigated, which had an area of 36,200 ha. Assuming that the forests are rotatively cultivated every 25 to 30 years, the total deforestation area is 6,870-6,948 ha in 25 years and 8,244~8,337 ha in 30 years. This result means that the balance between forest biomass and utilization is not in crisis, however, this balance might be lost as long as substitutive energy such as electricity is not supplied.

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ASSESSMENT OF INDOOR ENVIRONMENTAL QUALITY AND OCCURRENCE OF SICK BUILDING SYNDROME IN SMALL OFFICES IN PENANG, MALAYSIA

Jurnal Teknologi ◽

10.11113/jt.v75.4997 ◽

2015 ◽

Vol 75 (5) ◽

Author(s):

Ang Qiu Mei ◽

Md Azree Othuman Mydin

Keyword(s):

Environmental Quality ◽

Sick Building Syndrome ◽

Quality Measurement ◽

Comfort Level ◽

Working Environment ◽

Indoor Environmental Quality ◽

Sick Building ◽

The Difference

This study was done to investigate the relationship between indoor environmental quality and prevalence of Sick Building Syndrome in six small offices inPenangIsland. Indoor environmental quality measurement was conducted according to relevant standards. There are totally Sixty workers were selected to participate in an electronic questionnaire survey. Questionnaire was used to record the comfort level of respondents in the case studies and level of sick building syndrome faced by respondents. Through indoor environmental quality measurement, it is found that most of the offices facing the lighting and noise problem. The result from the questionnaire shows that in overall, the occupants satisfy with their working environment in term of indoor environmental quality although the result also shows the opinions of occupants on dissatisfaction on certain indoor environmental parameter according to case study. The study also found that most of the occupants feel drowsy and fatigue when they work within the offices. Besides, due to the difference of the indoor environmental quality of the buildings, the occupants are suffered from different symptoms of the sick building syndrome.

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