Publications by Niklaus Johner

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In this thesis we address the description of electrical transport properties of disordered conductor-insulator composites, mostly by numerical Monte Carlo simulations and analytical study of realistic tunnelling-percolation models. Such composites are basi ...

We present an in-depth analysis of the geometrical percolation behavior in the continuum of random assemblies of hard oblate ellipsoids of revolution. Simulations were carried out by considering a broad range of aspect-ratios, from spheres up to aspect-rat ...

The tunneling-percolation mechanism of conduction in disordered conductor-insulator composites is studied for a realistic continuum model where conducting and impenetrable spherical particles are dispersed in a three-dimensional continuum insulating materi ...

In order to cope with sustainable development policy, buildings should be at least healthy, comfortable and energy efficient. Criteria for assessing individually the occupant's perceived health, the provided thermal, visual, acoustical comfort, the indoor ...

Thick-film materials are very advantageous for piezoresistive pressure and force sensors because of ease of processing, reliability and low cost. The standard substrate material used with thick-film technology for sensing is alumina, but its elastic modulus is high and its strength rather low. Steels offer better mechanical properties and permit assembly without an elastomer seal, which is required for pressure sensing in severe conditions. In order to use the steel as substrate, the standard firing tempera

Performance of piezoresistive thick-film pressure sensors on steel substrates is hindered by the high required firing temperatures of the layers, which cause degradation of the substrate mechanical properties. Special steels or alloys that are relatively unaffected by these temperatures are available, but their cost is very high. A much more promising alternative is the reduction of the thick-film firing temperature, in order to allow application of the standard high-strength steels used in thin-film cells.

We report on our Monte Carlo calculations of the conductivity of monosized and conducting spherical particles dispersed in a homogeneous matrix, with interparticle transport mechanism given by electron tunneling. We show that our numerical results can be r ...

Within the European research project Health Optimisation Protocol for Energy-efficient Building (HOPE), 96 apartment buildings and 64 office buildings (of which approximately 75% have been designed to be energy-efficient) were investigated. The building ch ...

Piezoresistive pressure sensors using classical deformable structures such as membranes progressively run into difficulties at very high pressures (above 1 to 2 kbar), due to the decreasing ratio between the available sensing strain on the outer membrane surface and the maximal materials strain experienced on the pressurised side. Therefore, a novel "isostatic" pressure sensor concept, whereby the sensing element is immersed in the pressure fluid, has been developed. This method in principle allows the meas

We evaluate the percolation threshold values for a realistic model of continuum segregated systems, where random spherical inclusions forbid the percolating objects, modellized by hard-core spherical particles surrounded by penetrable shells, to occupy lar ...

We investigate the tunneling-percolation mechanism of DC transport nonuniversality for conducting particles of diameter Φ placed in series within the bonds of length Lof a regular lattice model. When L/Φ→∞ the resulting bond conductance distribution functi ...

Within the European research project HOPE, 64 office buildings were audited regarding in-door environment quality and building characteristics. Of those buildings, two groups are se-lected: 21 buildings with low prevalence of the sick building syndrome, an ...

In this work we study in more details the impact of voltage trimming on different characteristics of model thick-film resistors (TFRs). Two series of RuO2-based TFRs with different conducting grain sizes are studied. As the composition of model pastes is c ...

The ring-on-ring bending principle allows the fabrication of simple, low-cost thick-film piezoresistive sensors for compressive forces in the 10 to 400 N range. However some imperfections are encountered in its basic embodiment, such as relatively high for ...

In this work we seek to better understand the mechanisms governing pulse voltage trimming in disordered conductor-insulator composites. Therefore, we investigate the effect of the composition of thick-film resistors (TFRs) on sensitivity to high voltage pu ...

Within the European research project HOPE, 67 office buildings and 97 residential ones were investigated using checklists addressing the building characteristics and questionnaires to the occupants asking their perceived comfort (thermal visual, acoustical ...

We formulate a generalized tunneling-percolation model that describes the electrical properties of conductor-insulator cellular disordered systems. This model predicts and explains the experimentally observed universal and nonuniversal behaviors of such pr ...

Niklaus Johner

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On the origin of transport non-universality and piezoresistivity in segregated conductor-insulator composites and application to thick-film resistors

Percolative properties of hard oblate ellipsoids of revolution with a soft shell

Transport exponent in a three-dimensional continuum tunneling-percolation model

Multicriteria analysis of health, comfort and energy-efficiency of buildings

Piezoresistive properties of low-firing temperature thick-films on steel sensors

High performance low-firing temperature thick-film pressure sensors on steel

Electron tunneling in conductor-insulator composites with spherical fillers

Perceived health and comfort in relation to energy use and building characteristics

LTCC ultra high isostatic pressure sensors

Optimal percolation of disordered segregated composites

Apparent nonuniversality in finite segregated tunneling-percolaiton models

Sick Building Syndrome and Building Characteristics

Study of the impact of high-voltage trimming on several characteristics of model TFRs and their stability

Optimisation of a Thick-Film 10...400 N Force Sensor

High-Voltage Sensitivity Studies of Model Thick-Film Resistors

Correlations between SBS, perceived comfort, energy use and other building characteristics in european office and residential buildings

Piezoresistivity and tunneling-percolation transport in apparently nonuniversal systems

Multicriteria analysis methodology of IEQ energy use for sustainable buildings

Multicriteria analysis methodology of IEQ energy use for sustainable buildings