Consistency in Aggregation / Aggregationskonsistenz

2004 ◽  
Vol 224 (4) ◽  
Author(s):  
Ludwig von Auer
Keyword(s):  
Price Index ◽  
Price Change ◽  
Economic Research ◽  
Index Formula ◽  
Weak Consistency ◽  
Two Stage ◽  
Consistency Test ◽  
Multi Stage ◽  
Screening Device ◽  
Index Formulas

SummaryIn empirical economic research, individual prices are often aggregated into average prices of subaggregates. Then, these average prices are aggregated to produce the average price of the total aggregate. Often, such two stage procedures help to illuminate the underlying forces driving the overall result. Since price data are usually published as price changes, this two stage aggregation is typically based on some price index formula. In this paper, various screening devices are introduced which help to differentiate between suitable and unsuitable formulas. It is argued that testing for weak consistency in aggregation is a particularly important screening device. If a price index formula fails the weak consistency test and, nevertheless, this formula is used for a multi stage price index computation, then the measured overall price change depends on the number of computational stages and also on the precise manner in which the elementary items are partitioned into subaggregates. In other words, the findings are not robust and cannot be considered as particularly reliable. Based on these screening devices, it is examined which price index formulas can be expected to produce consistent results.

scholarly journals Generalized optimizations of two-stage forging of micro/meso copper fastener

2018 ◽  
Vol 185 ◽  
pp. 00002
Author(s):  
Shih-Hsien Lin ◽  
Un-Chin Chai ◽  
Gow-Yi Tzou ◽  
Dyi-Cheng Chen
Keyword(s):  
Simulation Analysis ◽  
Effective Strain ◽  
Cold Forging ◽  
Two Stage ◽  
Forming Simulation ◽  
Multi Stage ◽  
Element Simulation ◽  
Die Stress ◽  
Stress Optimization ◽  
Forging Force

Three are generalized simulation optimizations considering the forging force, the die stress, and the dual-goals in two-stage forging of micro/meso copper fastener. Constant shear friction between the dies and workpiece is assumed to perform multi-stage cold forging forming simulation analysis, and the Taguchi method with the finite element simulation has been used for mold-and-dies parameters design simulation optimizations considering the forging force, die stress, and dual-goals. The die stress optimization is used to explore the effects on effective stress, effective strain, velocity field, die stress, forging force, and shape of product. The influence rank to forging process of micro/meso copper fastener for three optimizations can be determined, and the optimal parameters assembly consider die stress can be obtained in this study. It is noted that the punch design innovation can reduce the forging force and die stress.

Dealing with Inaccurate Measures of Size in Two-Stage Probability Proportional to Size Sample Designs: Applications in African Household Surveys

2020 ◽  
Author(s):  
Graham Kalton ◽  
Ismael Flores Cervantes ◽  
Carlos Arieira ◽  
Mike Kwanisai ◽  
Elizabeth Radin ◽  
...  
Keyword(s):  
Final Stage ◽  
Population Based ◽  
Equal Probability ◽  
Household Surveys ◽  
Sample Design ◽  
African Countries ◽  
Two Stage ◽  
Fixed Sample ◽  
Multi Stage ◽  
Weighting Adjustments

Abstract The units at the early stages of multi-stage area samples are generally sampled with probabilities proportional to their estimated sizes (PPES). With such a design, an overall equal probability (EP) sample design would yield a constant number of final stage units from each final stage cluster if the measures of size used in the PPES selection at each sampling stage were directly proportional to the number of final stage units. However, there are often sizable relative differences between the measures of size used in the PPES selections and the number of final stage units. Two common approaches for dealing with these differences are: (1) to retain a self-weighting sample design, allowing the sample sizes to vary across the sampled primary sampling units (PSUs) and (2) to retain the fixed sample size in each PSU and to compensate for the unequal selection probabilities by weighting adjustments in the analyses. This article examines these alternative designs in the context of two-stage sampling in which PSUs are sampled with PPES at the first stage, and an equal probability sample of final stage units is selected from each sampled PSU at the second stage. Two-stage sample designs of this type are used for household surveys in many countries. The discussion is illustrated with data from the Population-based HIV Impact Assessment surveys that were conducted using this design in several African countries.

scholarly journals A Review on Anaerobic Co-Digestion with a Focus on the Microbial Populations and the Effect of Multi-Stage Digester Configuration

Energies ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 1106 ◽  
Author(s):  
Anahita Rabii ◽  
Saad Aldin ◽  
Yaser Dahman ◽  
Elsayed Elbeshbishy
Keyword(s):  
Anaerobic Digestion ◽  
Microbial Population ◽  
System Stability ◽  
Microbial Consortia ◽  
Microbial Populations ◽  
Stage Versus ◽  
Two Stage ◽  
Waste Sludge ◽  
Multi Stage ◽  
Mode A

Recent studies have shown that anaerobic co-digestion (AnCoD) is superior to conventional anaerobic digestion (AD). The benefits of enhanced bioenergy production and solids reduction using co-substrates have attracted researchers to study the co-digestion technology and to better understand the effect of multi substrates on digester performance. This review will discuss the results of such studies with the main focus on: (1) generally the advantages of co-digestion over mono-digestion in terms of system stability, bioenergy, and solids reduction; (2) microbial consortia diversity and their synergistic impact on biogas improvement; (3) the effect of digester mode, i.e., multi-stage versus single stage digestion on AnCoD. It is essential to note that the studies reported improvement in the synergy and diverse microbial consortia when using co-digestion technologies, in addition to higher biomethane yield when using two-stage mode. A good example would be the co-digestion of biodiesel waste and glycerin with municipal waste sludge in a two-stage reactor resulting in 100% increase of biogas and 120% increase in the methane content of the produced biogas with microbial population dominated by Methanosaeta and Methanomicrobium.

Genetic Algorithm to Solve Multi-Period, Multi-Product, Bi-Echelon Supply Chain Network Design Problem

2009 ◽  
Vol 2 (4) ◽  
pp. 24-42 ◽  
Author(s):  
R. Dhanalakshmi ◽  
P. Parthiban ◽  
K. Ganesh ◽  
T. Arunkumar
Keyword(s):  
Supply Chain ◽  
Supply Chains ◽  
Raw Materials ◽  
Optimization Techniques ◽  
Network Design Problem ◽  
Production Plant ◽  
Two Stage ◽  
Cost Structures ◽  
Multi Stage ◽  
Product Costs

In many multi-stage manufacturing supply chains, transportation related costs are a significant portion of final product costs. It is often crucial for successful decision making approaches in multi-stage manufacturing supply chains to explicitly account for non-linear transportation costs. In this article, we have explored this problem by considering a Two-Stage Production-Transportation (TSPT). A two-stage supply chain that faces a deterministic stream of external demands for a single product is considered. A finite supply of raw materials, and finite production at stage one has been assumed. Items are manufactured at stage one and transported to stage two, where the storage capacity of the warehouses is limited. Packaging is completed at stage two (that is, value is added to each item, but no new items are created), and the finished goods inventories are stored which is used to meet the final demand of customers. During each period, the optimized production levels in stage one, as well as transportation levels between stage one and stage two and routing structure from the production plant to warehouses and then to customers, must be determined. The authors consider “different cost structures,” for both manufacturing and transportation. This TSPT model with capacity constraint at both stages is optimized using Genetic Algorithms (GA) and the results obtained are compared with the results of other optimization techniques of complete enumeration, LINDO, and CPLEX.

Structure and Propagation of Rotating Stall in a Single- and a Multi-Stage Axial Compressor

1999 ◽  
Author(s):  
H. M. Saxer-Felici ◽  
A. P. Saxer ◽  
F. Ginter ◽  
A. Inderbitzin ◽  
G. Gyarmathy
Keyword(s):  
Numerical Solutions ◽  
Equations Of Motion ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Water Model ◽  
Two Stage ◽  
Additional Information ◽  
Driving Mechanisms ◽  
Multi Stage ◽  
Stall Cells

The structure and propagation of rotating stall cells in a single- and a two-stage subsonic axial compressor is addressed in this paper using computational and experimental analysis. Unsteady solutions of the 2-D inviscid compressible (Euler) equations of motion are presented for one operating point in the fully-developed rotating stall regime for both a single- and a two-stage compressor. The inviscid assumption is verified by comparing the single-stage 2-D in viscid/compressible solution with an equivalent 2-D viscous (Navier-Stokes) result for incompressible flow. The structure of the rotating stall cell is analyzed and compared for the single- and two-stage cases. The numerical solutions are validated against experimental data consisting of flow visualization and unsteady row-by-row static pressure measurements obtained in a four-stage water model of a subsonic compressor. The CFD solutions supply a link between the observed experimental features and provide additional information on the structure of the stall flow. Based on this study. supporting assumptions regarding the driving mechanisms for the propagation of fully-developed rotating stall cells and their structure are postulated. In methodical respect the results suggest that the inviscid model is able to reproduce the essentials of the flow physics associated with the propagation of fully-developed, full-span rotating stall in a subsonic axial compressor.

Moisture Content and Physical Properties of High-Moisture Agricultural Material Dried by Impinging Stream Dryer

2017 ◽  
Vol 728 ◽  
pp. 347-352
Author(s):  
Chatchai Nimmol ◽  
Thawatchai Kaewkamrop
Keyword(s):  
Moisture Content ◽  
Physical Properties ◽  
Feed Rate ◽  
High Moisture ◽  
Two Stage ◽  
Color Changes ◽  
Multi Stage ◽  
Short Period ◽  
Drying Conditions ◽  
Agricultural Material

The objective of this research was to study the drying of high-moisture agricultural material using an impinging stream dryer with multi-stage drying concept. Okara was used in this study as the test agricultural material. Experiments were performed in one-stage and two-stage drying. The final moisture content of the okara at several drying conditions was examined. The physical properties of dried okara were analyzed in terms of color and rehydration ability. It was found from the experiment that with the use of multi-stage drying concept the moisture content of okara could be significantly reduced within a very short period of time. In terms of physical properties, it was observed that the dried okara was darker, redder and more yellow than the fresh okara. Drying at higher temperatures led to higher color changes values of the dried okara. The effect of okara feed rate on the redness and yellowness was not significant, except for the lightness; drying at lower okara feed rates led to a darker dried okara. An increase in the drying temperature and a decrease in the okara feed rate led to a higher rehydration ability of the okara.

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