Developable Surface

Variable rainfall distribution and terrain make surface water harvesting and storage a challenge in many developing countries. The overall goal of this study is to collect and develop information required to equip extension, non-governmental organization (NGO) agents, contractors and engineers for surface water development and aquaculture enterprise development in Honduras and Latin America. A pond water balance for the levee production pond enabling determination of water flow required to balance seepage, evaporation and direct rainfall was developed in English and Spanish on the Microsoft Excel ® platform. The pump-in flow rate can also be determined for reaching a volume change per month target. A second model was formulated for evaluating surface water capture by watershed and/or hillside ponds for meeting the levee pond demand. Using hillside ponds that fill by impounding a fraction of total runoff (e.g., diverting water upstream) from streams appears to have promise for meeting water needs. A systematic approach using both models to reach a sustainable water supply target emerged from this work. Both the levee pond model and the water harvest model are based on balancing inputs and outputs given monthly rainfall patterns. A simple approach to mechanical spillways preliminary design was developed. The models are adaptable to any location if key input data is available, particularly average monthly rainfall and storm frequency-duration data. The models do not address water quality issues. The software is intended for watershed sizes not larger than 500 ha and storage ponds of less than 5 ha surface area-4 m depth due to relationship limitations and safety concerns. Coupling with other cooperative development concerns such as marketing

New image processing methods and active photonics apparatus have made possible the development of relatively inexpensive optical systems for complex shape and object measurements. We present dynamic 360° scanning method for analysis of human lower body biomechanics, with an emphasis on the analysis of the knee joint. The anatomical structure (of high medical interest) that is possible to scan and

Microelectromechanical system (MEMS) microswitches are receiving increasing attention, particularly in the RF community. Low power consumption, low insertion loss, high isolation, excellent linearity, and the ability to be integrated with other electronics all make microswitches an attractive alternative to other mechanical and solid-state switches. This article features a newly developed, surface micromachined, electrostatically actuated direct metal-to-metal microswitch which can be used in applications from dc through microwave.

Fascinating and elegant shapes may be folded from a single planar sheet of material without stretching, tearing or cutting, if one incor- porates curved folds into the design. We present an optimization- based computational framework for design and digital reconstruc- tion of surfaces which can be produced by curved folding. Our work not only contributes to applications in architecture and

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 844-854 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Dental implants Surface roughness Nano-sized topography Biomimetic calcium phosphate coating a b s t r a c t

Figure 1: Top left: Reconstruction of a car model based on a felt design by Gregory Epps. Close-ups of the hood and the rear wheelhouse are shown on the left. The fold lines are highlighted on the car's development. Top right and bottom: Architectural design. All shown surfaces can be isometrically unfolded into the plane without cutting along edges and can thus be texture mapped without any seams or distortions.

In this experimental study some statistical calculations have been made to eliminate quality problems such as undesirable tolerance limits and out of circularity of spherodial cast iron parts during machining. X-R control charts have been constructed on the data obtained from this manufacturing to discover and correct assignable causes, so that the machine capability (Cp) and the process capability (Cpk) can be determined.

Osservando la quadratura sulla volta della chiesa di San Matteo (affrescata tra 1717 e 1719 da Giuseppe e Francesco Melani) si notano alcune difformità. Né i basamenti né le cornici degli ordini disegnati seguono del tutto l’andamento di quei reali, ma a volte sembrano “salire” o “scendere” rispetto alle cornici della chiesa. Le cornici che reggono le balconate in aggetto, come le loro balaustre, assumono una forma molto insolita. Queste due curve, quando osservate dal punto di vista privilegiato, non si percepiscono né come circolari né come ovali, e in più, non sono nemmeno parallele tra di loro. Le rette verticali (perpendicolari al quadro) sembrano curvare in alcuni punti.
Il presente studio si pone di esaminare alcuni punti “incongrui” di questa quadratura sulla base di un rilievo integrato (scansione laser e fotogrammetria), concentrandosi su due principali passaggi creativi:
1. Come si fa a “progettare” il bozzetto piano per uno spazio così irregolare? L’architettura pensata per la volta segue veramente la geometria irregolare della chiesa (trapezio scaleno), oppure usa vari accorgimenti per adattare un modello a pianta rettangolare sulla base esistente?
2. In che maniera avviene il trasferimento del bozzetto piano sulla superfice complessa della volta?
In quanto riguarda la progettazione del bozzetto, l’altezza ricostruita dell’architettura dipinta sembra fornirci il primo indizio. Essa è pari alla distanza che sta tra il punto di vista e l’imposta della volta. Questa particolare altezza si rileva come molto “comoda” dal punto di vista operativo in un metodo (per fare bozzetti) descritto dal geografo veneziano Cristoforo Sorte. Tale metodo comporta l’uso di un modello in scala, di ciò che si vuole dipingere, ed uno specchio piano posto alla base del modello. Se l’occhio è posto all’altezza del modello nella fase di disegno l’altezza del architettura dipinta sarà la stessa nella ricostruzione (ovviamente in scala). Un’altezza maggiore invece obbligherebbe l’occhio ad entrare dentro il modello (posizione scomoda).
Il secondo passaggio, cioè il trasferimento dal bozzetto piano sulla superficie voltata, in linea di principio, potrebbe avvenire in due modi:
-Il primo sarebbe una specie di proiezione del bozzetto piano posto all’imposta della volta sulla superficie curva dal punto di vista, come suggerito da Andrea Pozzo. Questo metodo (se fatto dal vero e non sul modello in scala), non creerebbe le difformità del disegno dovute alla geometria irregolare della volta. Osservate dal punto di vista tutte le difformità svanirebbero.
-L’altro metodo possibile potrebbe essere quello di costruire un corrispondente modello in scala della volta, proiettare sul esso la griglia del bozzetto e riportarne lo sviluppo delle linee meccanicamente su fogli di carta. Una volta ingrandita la griglia, si prosegue con il disegno di altri elementi principali dell’architettura da dipingere, direttamente sui cartoni ingranditi.  In questo caso, le difformità della volta reale, che forse non sono state rilevate e riprodotte nel fare il modellino, risalterebbero fuori e sarebbero evidenti quando osservate dal punto di vista.
Nel caso di San Matteo, si rilevano alcuni segni che diventano improvvisamente “regolari” nella proiezione sviluppata. Questa operazione farebbe riferimento ad una cultura molto attenente alla cartografia e ai problemi legati alle superfici non sviluppabili, alla quale non interessa più soltanto l’inganno ma vuole mettere altre pratiche in atto.

Paper, sheet metal, and many other materials are approximately unstretchable. The surfaces obtained by bending these materials can be flattened onto a plane without stretching or tearing. More precisely, there exists a transformation that maps the surface onto the plane, after which the length of any curve drawn on the surface remains the same. Such surfaces, when sufficiently regular, are well known to mathematicians as developable surfaces. While developable surfaces have been widely used in engineering, design and manufacture, they have been less popular in computer graphics, despite the fact that their isometric properties make them ideal primitives for texture mapping, some kinds of surface modelling, and computer animation. Unfortunately, their constrained isometric behaviour cuts across common surface formulations. We formulate a new developable surface representation technique suitable for use in interactive computer graphics. The feasibility of our model is demonstrated by applying it to the modelling of a hanging scarf and ribbons and bows. Possible extensions and interesting areas of further research are discussed.

: Conical meshes are planar quad meshes which discretize principal curvature lines, possess offset meshes at a constant distance as well as planar connecting elements supporting the offset meshes (left). Therefore they are especially suited for architectural design with glass structures (right). This design of a railway station by B. Schneider was generated by a subdivision-type process (see also Fig. 14).

Designing surfaces with antifouling and antimicrobial properties has an important route to solve problems, such as infections and fouling, in healthcare and industrial applications. Recently, there has been considerable interest in developing surfaces with polymers because of their distinct properties, such as their length scale, their processability, low cost, tunable properties, and diverse functionalities. This article reviews the polymer systems developed as antifouling-antimicrobial surface coatings, termed as biopassive and bioactive polymers respectively. Many different types of bioactive and biopassive polymeric systems and their limitations are presented.

Despite many synthetic biomaterials having physical properties that are comparable or even superior to those of natural body tissues, they frequently fail due to the adverse physiological reactions they cause within the human body, such as infection and inflammation. The surface modification of biomaterials is an economical and effective method by which biocompatibility and biofunctionality can be achieved while preserving the favorable bulk characteristics of the biomaterial, such as strength and inertness. Amongst the numerous surface modification techniques available, plasma surface modification affords device manufacturers a flexible and environmentally friendly process that enables tailoring of the surface morphology, structure, composition, and properties of the material to a specific need. There are a vast range of possible applications of plasma modification in biomaterial applications, however, the focus of this review paper is on processes that can be used to develop surface morphologies and chemical structures for the prevention of adhesion and proliferation of pathogenic bacteria on the surfaces of in-dwelling medical devices. As such, the fundamental principles of bacterial cell attachment and biofilm formation are also discussed. Functional organic plasma polymerised coatings are also discussed for their potential as biosensitive interfaces, connecting inorganic/metallic electronic devices with their physiological environments.

The combination of fashion and transformation frames a current reality where the subjects and their dressing practices are the objects of processes of a constantly mutating identity building.
At the centre of the debate on fashion design there is always a human body which interacts and coexists with the technologies that inhabit it: they, at the same time, amplify the range of forms and operational possibilities based on the most advanced representation methods and prototyping of clothing and accessories, relating to innovative materials.
The paper reflects on the modes of construction of the artefacts and on the methods of planar development of patterns, needful for
the making of clothes and accessories, and at the same time investigates the inspiring principles of projects that relate with wefts traced directly on real bodies, or on their digital clones.
The main case studies here presented concern the work of fashion designers and creative directors who experiment with digital technologies during the ideation, design, pattern making and prototyping phases, up to the visual communication of fashion garments and accessories.
A complex kaleidoscope of free forms that fit moving bodies, in patterns and geometries that merge with the physicality of the subjects, and sometimes deny it, demonstrates that representation, in all its knowledge, is crucial in the fashion industry.

The technology of obtaining active carbon from anthracite mined in Siberia is described. The effect of the activating agent, anthracite/activator ratio and activation temperature has been tested. The activation either with KOH or NaOH has been found to lead to microporous active carbon samples of well-developed surface area reaching from 588 to 2260m2/g and pore volume from 0.29 to 1.12m3/g.

We report herein on extensive post-mortem analysis of rechargeable Li-ion batteries after prolonged cycling at 25 and 40 8C. The 18650-type batteries produced by standard procedure at LG Chem. Inc. were comprised of graphitic carbon anodes, LiCoO 2 cathodes, and a commercial, Li-battery grade ethylene carbonate, ethyl Á/methyl carbonate (EC-EMC)/LiPF 6 solution. The batteries were dismantled under highly pure inert atmosphere after prolonged cycling by a specially designed system, followed by analysis of both electrodes by SEM, XRD, FTIR, and electrochemical methods (voltammetry, impedance spectroscopy). The residual solution was analyzed by gas chromatography Á/high-resolution mass spectrometry (GCMS), and by Karl Fischer titration (for trace H 2 O content). It was found that the structure of both electrodes is basically retained during prolonged cycling. However, they developed surface films that considerably increase their impedance, thus badly affecting the battery performance after a few hundred charge Á/ discharge cycles. It also appears that part of the cathode's active mass became electronically isolated from the current collector. Hence, the impedance of both electrodes increases considerably upon cycling. The residual solutions contained 10 Á/15 times more water than the pristine solution, as well as products of trans -esterification of the alkyl carbonates, and some fluorinated and phosphorous-containing organic species. The surface chemistry of both electrodes seems to be dominated primarily by LiF formation. Capacity fading mechanisms of Li-ion batteries are discussed. #

ruled surfaces of degree 2m, whose shape is guided by m ϩ 1 control lines and m frame lines. This is an advantage In this paper, geometric design problems for rational ruled surfaces are studied. We investigate a line geometric control over the method of Ravani and Wang, which results in structure and its connection to the standard tensor product Bsurfaces of degree 3m from the same data.

Developable surfaces are modelled with pieces of right circular cones. These cone spline surfaces are well-suited for applications: They possess degree two parametric and implicit representations. Bending sequences and the development can be explicitly computed and the offsets are of the same type. The algorithms are based on elementary analytic and constructive geometry. There appear interesting relations to planar and spherical arc splines.

At present, nanoparticles are used for various biomedical applications where they facilitate laboratory diagnostics and therapeutics. More specifically for drug delivery purposes, the use of nanoparticles is attracting increasing attention due to their unique capabilities and their negligible side effects not only in cancer therapy but also in the treatment of other ailments. Among all types of nanoparticles, biocompatible superparamagnetic

d e n t a l m a t e r i a l s 2 3 ( 2 0 0 7 ) 844-854 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . i n t l . e l s e v i e r h e a l t h . c o m / j o u r n a l s / d e m a Dental implants Surface roughness Nano-sized topography Biomimetic calcium phosphate coating a b s t r a c t

Dual characterizations of the Bertrand offset-surfaces are given and some results are obtained in terms of their integral invariants. A new characterization of Bertrand offsets of developable surfaces is given. Moreover, some relationships between the area of projections of spherical images of Bertrand offsets of trajectory ruled surfaces and their integral invariants are obtained.In dieser Arbeit sind die dualen karakterizationen der geschlossenen Bertrandischen Trajectorenregelflächenpaaren gegeben und einige zugehorigen Resultate in der Art von Integralinvarianten erhalten. Weiter sind die Beziehungen zwischen der Projectionsflächeninhalten des Sphärischen Bildern dieser Flächen und deren Integralinvarianten gegeben.

Motivated by applications in architecture and manufacturing, we discuss the problem of covering a freeform surface by single curved panels. This leads to the new concept of semi-discrete surface representation, which constitutes a link between smooth and discrete surfaces. The basic entity we are working with is the developable strip model. It is the semi-discrete equivalent of a quad mesh with planar faces, or a conjugate parametrization of a smooth surface. We present a B-spline based optimization framework for efficient computing with D-strip models. In particular we study conical and circular models, which semi-discretize the network of principal curvature lines, and which enjoy elegant geometric properties. Together with geodesic models and cylindrical models they offer a rich source of solutions for surface panelization problems.

Since neural networks have been widely applied to the nonlinear transfer function approximation, we present an empirical neural network algorithm to estimate major parameters in surface waters from combined optical data and microwave data in the Gulf of Finland. Concurrent in situ surface water quality measurements, optical (Landsat TM) data and microwave (ERS-2 SAR) data were obtained in selected locations in August 1997. The TM and ERS-2 SAR data from locations of water samples were extracted and digital data were examined in numerous transformations. Although significant correlations were observed between digital data and chlorophyll-a (Chl-a), suspended sediment concentration (SSC), turbidity (Turb), and Secchi disk depth (SDD), application of neural networks appears to yield a superior performance in modeling transfer functions in this study area. Here, an empirical neural network algorithm is applied to estimate the transfer functions between the major characteristics of surface waters and the satellite optical and microwave data. The results show that the estimation accuracy for major characteristics of surface waters using the neural network is much better than those from regression analysis. The results also indicate that microwave data can assist to improve the estimation of these characteristics. Therefore, it may be possible to develop surface water quality algorithms in which microwave data are used as supplementary data to optical observations. However, this improvement of optical data retrieval algorithm is limited in this case study. The technique still needs to be refined in detail in order to detect differences within the typical range of these water quality parameters found in the area under study. D 2002 Elsevier Science Inc. All rights reserved. 0034-4257/02/$ -see front matter D 2002 Elsevier Science Inc. All rights reserved. PII: S 0 0 3 4 -4 2 5 7 ( 0 2 ) 0 0 0 0 9 -3

Reliable and repeatable field sampling methods are needed for monitoring ecosystem optical properties linked to carbon flux. Here we describe a tram system, consisting of a dual-detector spectrometer mounted on a robotic cart for mobile sampling of ecosystem spectral reflectance. To illustrate the application of this system for monitoring dynamic ecosystem activity, we illustrate how the tram can be used for exploring the multiple factors influencing the Normalized Difference Vegetation Index (NDVI), a measure of vegetation greenness and a key optical indicator of vegetation carbon dioxide assimilation. With this system, we collected five years of NDVI data for a chaparral ecosystem in Southern California subject to extreme disturbance. Key factors affecting NDVI at this site included snow cover, sky conditions (clear vs. cloudy), time of day, season, species composition, and environmental perturbations such as rainfall, drought and fire. Applications of this tram system include ecosystem monitoring, satellite validation, and developing surface-atmosphere flux models from remote sensing.

Various dynamic soil chemistry models have been developed to gain insight into impacts of atmospheric deposition of sulphur, nitrogen and other elements on soil and soil solution chemistry. Sorption parameters for anions and cations are generally calibrated for each site, which hampers extrapolation in space and time. On the other hand, recently developed surface complexation models (SCMs) have been successful in predicting ion sorption for static systems using generic parameter sets. This study reports the inclusion of an assemblage of these SCMs in the dynamic soil chemistry model SMARTml and applies this model to a spruce forest site in Solling Germany. Parameters for SCMs were taken from generic datasets and not calibrated. Nevertheless, modelling results for major elements matched observations well. Further, trace metals were included in the model, also using the existing framework of SCMs. The model predicted sorption for most trace elements well.

Experiments were conducted to examine soil erosion by headcut development and upstream migration in rills typical of upland areas. Soil material, simulated rain, overland flow discharge, and initial headcut height were held constant in each experiment, but initial slope of the bed varied from 1% to 10%. Air-dried, crushed, and sieved sandy loam to sandy clay loam soil was incrementally packed into a laboratory channel 2 m long and 0.165 m wide to a depth of 0.25 m. Soil bulk density was 1425 kg m y3 in each experiment. A pre-formed headcut 25-mm high was constructed 1.5 m downstream of the entrance of the flume. Simulated rain, applied at 21 mm h y1 for 4 h, produced a well-developed surface seal that minimized the detachment of the surface soil. Following the rainfall, overland flow at a rate of 52 l min y1 was released onto the bed, soil erosion occurred at the pre-formed headcut overfall, and a scour hole developed, enlarged, and migrated upstream. The rate of headcut migration was constant within each experiment, but higher slopes of the bed generally resulted in lower rates of migration. At slopes on the bed of 2% and smaller, the overfall nappe at the headcut brinkpoint remained submerged, and a steady-state condition was achieved: sediment yield and geometry of the scour hole remained constant as the headcut migrated upstream. For slopes on the bed of 3% and greater, the overfall nappe became aerated, and as the headcut migrated upstream, the depth of scour increased. Higher slopes on the bed resulted in deeper scour holes. Mechanisms of soil erosion included the formation of tension cracks and seal removal at the headcut brinkpoint, soil washout along the aerated headcut face, and plunge-pool scour. The slope of the sediment deposit downstream of the migrating headcut was 2.2% for all experiments, and suggests that flow discharge and not the initial slope of the bed controlled transport capacity and downstream adjustment of the bed. Published by Elsevier Science B.V.

The consequences of external sulfate attack were investigated by traditional test methods, i.e. length and mass change, as well as by a newly developed, surface sensitive ultrasonic method, using Leaky Rayleigh waves (1 MHz). The macroscopic changes are discussed and compared with thermodynamic calculations and microstructural findings (SEM/EDS). The results show that the main impact of limestone additions on resistance to sulfate degradation are physicali.e. addition of a few percent in Portland cement reduces the porosity and increases the resistance of Portland cement systems to sulfate; but higher addition of 25% increase porosity and lower resistance to sulfate. The kinetics of degradation were dramatically affected by the solution concentration (4 or 44 g Na 2 SO 4 /l) and the higher concentration also resulted in the formation of gypsum, which did not occur at the low concentration. However the pattern of cracking was similar in both cases and it appears that gypsum precipitates opportunistically in pre-formed cracks so it is not considered as making a significant contribution to the degradation. At 8°C limited formation of thaumasite occurred in the surface region of the samples made from cement with limestone additions. This thaumasite formation led to loss of cohesion of the paste and loss of material from the surface of the samples. However thaumasite formation was always preceded by expansion and cracking of the samples due to ettringite formation and given the very slow kinetics of thaumasite formation it was probably facilitated by the opening up of the structure due to ettringite induced cracking. The expansion of the samples showed a steady stage, followed by a rapidly accelerating stage, with destruction of the samples. The onset of the rapidly accelerating stage occurred when the thickness of the cracked surface layer reached about 1-1.5 mm-10-15% of the total specimen thickness (10 mm).

Superhydrophobic surfaces display water contact angles greater than 150°in conjunction with low contact angle hysteresis. Microscopic pockets of air trapped beneath the water droplets placed on these surfaces lead to a composite solid-liquid-air interface in thermodynamic equilibrium. Previous experimental and theoretical studies suggest that it may not be possible to form similar fully-equilibrated, composite interfaces with drops of liquids, such as alkanes or alcohols, that possess significantly lower surface tension than water (␥ lv ‫؍‬ 72.1 mN/m). In this work we develop surfaces possessing re-entrant texture that can support strongly metastable composite solid-liquid-air interfaces, even with very low surface tension liquids such as pentane (␥ lv ‫؍‬ 15.7 mN/m). Furthermore, we propose four design parameters that predict the measured contact angles for a liquid droplet on a textured surface, as well as the robustness of the composite interface, based on the properties of the solid surface and the contacting liquid. These design parameters allow us to produce two different families of re-entrant surfaces-randomly-deposited electrospun fiber mats and precisely fabricated microhoodoo surfaces-that can each support a robust composite interface with essentially any liquid. These omniphobic surfaces display contact angles greater than 150°and low contact angle hysteresis with both polar and nonpolar liquids possessing a wide range of surface tensions.

By its dual representation, a developable surface can be viewed as a curve of dual projective 3-space. After introducing an appropriate metric in the dual space and restricting ourselves to special parametrizations of the surfaces involved, we derive linear approximation algorithms for developable NURBS surfaces, including multiscale approximations. Special attention is paid to controlling the curve of regression.

In this article, we obtain all nonplanar cylindrical surfaces in the Minkowski space 3 1 with pointwise 1-type Gauss map of the second kind. We also prove that right circular cones and hyperbolic cones in 3 1 are the only cones in 3 1 with pointwise 1-type Gauss map of the second kind. We conclude that there is no tangent developable surface fully lying in 3 1 with pointwise 1-type Gauss map of the second kind.

This paper deals with the problem 'which knots or links in 3-space bound flat (immersed) compact surfaces?' In a forthcoming paper by the author, it is proven that any simple closed space curve can be deformed until it bounds a flat orientable compact (Seifert) surface. The main results of this paper are that there exist knots that do not bound any flat compact surfaces. The lower bound of total curvature of a knot bounding an orientable nonnegatively curved compact surface can, for varying knot types, be arbitrarily much greater than the infimum of curvature needed for the knot to have its knot type. The number of 3-singular points (points of zero curvature or if not then of zero torsion) on the boundary of a flat immersed compact surface is greater than or equal to twice the absolute value of the Euler characteristic of the surface. A set of necessary and, in a weakened sense, sufficient conditions for a knot or link to be what we call a generic boundary of a flat immersed compact surface without planar regions is given. : Primary 53A04; Secondary 53A05, 51L15.

This paper presents an attempt to make the alkaline electrolytic production of hydrogen more efficient by adding in situ activating compounds in ionic and complex form. Cobalt and tungsten based ionic activators (i.a.), added directly into the electrolyte during the electrolytic process, reduce energy requirements per mass unit of hydrogen produced for about 15%, compared to non-activated system, for a number of current densities in a wide temperature range. Energy saving is higher at higher temperatures and on higher current densities. Structural and morphological characteristic of deposit formed on the cathode during the electrolytic process reveal very interesting and unique pattern with highly developed surface area and uniform distribution of the pores. Obtained deposit also exhibit a long term stability.

This paper presents aspects related to the generation and tracking of closed trajectories over an arbitrary surface of unknown geometry. Such a capacity is required in some of the most important industrial robotic tasks, like the cutting or welding of commercial plates. Previous work has shown how a calibration-free, vision-based method can be combined with an optimal geodesic-mapping approach, in order to generate an optimal trajectory that traces a previously defined path, stored as a CAD model, over an arbitrary, curved surface. The application of this technique in the case of nondevelopable surfaces did not achieve closure when a closedtrajectory was attempted. This paper presents a methodology for successfully achieving closure of a given closed-path, when this is traced over a non-developable surface. The proposed technique was tested using an industrial robot and a visionbased system that included structured lighting for imageanalysis simplification. The results of these experiments are reported herein.

This paper presents an attempt to make the alkaline electrolytic production of hydrogen more efficient by adding in situ activating compounds in ionic and complex form. Cobalt and tungsten based ionic activators (i.a.), added directly into the electrolyte during the electrolytic process, reduce energy requirements per mass unit of hydrogen produced for about 15%, compared to non-activated system, for a number of current densities in a wide temperature range. Energy saving is higher at higher temperatures and on higher current densities. Structural and morphological characteristic of deposit formed on the cathode during the electrolytic process reveal very interesting and unique pattern with highly developed surface area and uniform distribution of the pores. Obtained deposit also exhibit a long term stability.

We present a novel and effective method for modeling a developable surface to simulate paper bending in interactive and animation applications. The method exploits the representation of a developable surface as the envelope of rectifying planes of a curve in 3D, which is therefore necessarily a geodesic on the surface. We manipulate the geodesic to provide intuitive shape control for modeling paper bending. Our method ensures a natural continuous isometric deformation from a piece of bent paper to its flat state without any stretching. Test examples show that the new scheme is fast, accurate, and easy to use, thus providing an effective approach to interactive paper bending. We also show how to handle non-convex piecewise smooth developable surfaces.

Studies from U.S. and Russian literature on experimental and theoretical investigations of thermionic converters with developed emitter surfaces are reviewed and analyzed. Experimental data for these converters is compared with that for close-spaced and traditional Cs arc converters. The former is most advantageous at low temperatures from 1300 to 1700 K, with the power gain increasing as the emitter temperature decreases and/or its emission properties deteriorate. This power gain is attainable at a larger load voltage and significantly larger optimum interelectrode gap size than traditional converters. Additional experiments and mathematical modeling are needed to understand the physical processes taking place and assess the performance of thermionic converters with developed emitter surfaces as compared to traditional ones operating under identical conditions. 0 1997 Elsevier Science Ltd. All rights reserved Thermionic converter Developed surface emitter Work function Plasma voltage drop PARAMONOV and EL-GENK: CESIUM THERMIONIC CONVERTERS 547

In this experimental study some statistical calculations have been made to eliminate quality problems such as undesirable tolerance limits and out of circularity of spherodial cast iron parts during machining. X–R control charts have been constructed on the data obtained from this manufacturing to discover and correct assignable causes, so that the machine capability (Cp) and the process capability (Cpk) can be determined.
In order to compare design tolerance on working drawings and attained tolerances on workpieces after machining five mass production lines were set up in a medium sized company. The results obtained from five X–R control charts and the data gathered from all production lines were processed and evaluated. At this stage of the study, it was observed that some parts were oval and out of tolerance limits, machines and processes were insufficient and production was instable. Through machining data and follow up studies some assignable causes for faulty workpieces were discovered, and ovalness and out of tolerance limits problems were eliminated. In addition to these developments, surface roughness of machined workpieces was improved.

All these activities show that in small or medium sized companies statistical quality control can be useful component of production provided that sufficient finance and qualified personal are utilized.