Bonded thick film SOI with pre-etched cavities

We have studied direct bonding and thinning of pre-etched silicon wafers. Silicon-on-insulator (SOI) substrates with pre-etched cavities provide freedom to MEMS design and enable manufacturing of advanced sensor structures (sensor structures that would be difficult or impossible with conventional substrates). Cavities with different shapes and sizes were etched on to the handle wafers. The etched handle wafers were bonded to unpatterned cap wafers in air or in vacuum. The bonding quality was evaluated with scanning acoustic microscopy and with HF-etching test. After bonding, the cap wafers were thinned down with grinding and polishing. The thickness variation of silicon diaphragm over the cavities was evaluated with cross-sectional SEM. The deflection of the Si film was measured with surface profilometry. To decrease the deflection and the thickness variation of the film, different support structures were placed inside the cavities.The bonding experiments carried out with patterned wafers showed that vacuum bonding results in slightly higher bonding energy than bonding in air. With large cavity fraction (80% of total wafer area), the air bonded samples had large void on the bonded interface. With smaller cavity fractions or with vacuum bonded samples, no such voids were found. Thinning studies showed that the thickness variation of the silicon diaphragm increases with increasing cavity dimensions and with decreasing SOI layer thickness. Thickness variation can be reduced with support structures under the Si membrane.     

Daylight optimization of multifunctional solar facades

Multifunctional solar facades consisting of a transparent window and an opaque photovoltaic section are analyzed and optimized. Employing numerical daylight estimation techniques, the optimal shape, position, and area of the window section is determined. Maximum yearly average daylight availability is achieved with a similarly shaped window as the facade which is placed near the centre of the facade. For non-residential buildings, the yearly average useful interior daylight illuminance does not increase significantly for windows larger than 30% of the total facade area. Considering both the artificial lighting requirement replaced by daylight through the window and the electricity produced by the PV section of the facade, the maximum electricity benefit for a south-facing facade is achieved with a window area of about 10% of the total facade area in Southern Europe (38° N) and 15% in Northern Europe (60° N).     

Modeling the effectiveness of oil combating from an ecological perspective--a Bayesian network for the Gulf of Finland; the Baltic Sea

Maritime traffic poses a major threat to marine ecosystems in the form of oil spills. The Gulf of Finland, the easternmost part of the Baltic Sea, has witnessed a rapid increase in oil transportation during the last 15 years. Should a spill occur, the negative ecological impacts may be reduced by oil combating, the effectiveness of which is, however, strongly dependent on prevailing environmental conditions and available technical resources. This poses increased uncertainty related to ecological consequences of future spills. We developed a probabilistic Bayesian network model that can be used to assess the effectiveness of different oil combating strategies in minimizing the negative effects of oil on six species living in the Gulf of Finland. The model can be used for creating different accident scenarios and assessing the performance of various oil combating actions under uncertainty, which enables its use as a supportive tool in decision-making. While the model is confined to the western Gulf of Finland, the methodology is adaptable to other marine areas facing similar risks and challenges related to oil spills.     

Nanocrystalline WC-Co HVAF Coatings by Utilizing Novel Powder Manufacturing Route Using Water-Soluble Raw Materials

In this study, nanostructured WC-Co coatings were produced using experimental nanocrystalline WC-12Co and WC-24Co powders produced by a novel chemical synthesis route. Test coatings were produced using HVAF spraying keeping the temperature as low as possible during the deposition in order to avoid decomposition of the nanocarbides. In experimental powders, two different Co incorporation methods were used: a conventional way in which cobalt was incorporated as a metallic Co powder and a chemical synthesis way in which cobalt acetate was used as a cobalt source. When using cobalt acetate, it decomposes to metallic cobalt during the process. Experimental powders in which cobalt acetate has been used as cobalt source resulted poor deposition efficiency. With warmer parameters, powders resulted better DE, but significant WC decarburization and the dissolution into the matrix phase occurred. Powders in which Co has been introduced as Co powder showed enhanced DE enabling spraying with decreased temperature and higher particle velocity, resulting in coatings with less WC decomposition. Especially, an experimental powder in which Co has been incorporated both as Co powder and as Co-Ac results very fine nanocarbide structure with significantly less WC decomposition having a hardness value of 1201 HV0.3, even with 24% Co.     

The insufficiency of Pigouvian taxes in a spatial general equilibrium model

The paper considers, in a spatial general equilibrium setting, the pollution externality problem caused by a competitive industry. It is shown that the pollution control instrument supporting the optimum is a two-part Pigouvian tax–emission rights scheme in which the polluter pays only for the emissions which exceed its initial emission rights. The optimal level of the emission rights depends on the nature of pollution. In the global pollution case they are zero, whereas in the local pollution case they are equal to the firm's emissions at the optimum. In general, the optimal initial emission rights are between these values, but they may also be negative. In the latter case the firm pays for a greater amount of emissions than it emits. The emission tax proceeds, if there are any, must be distributed to the victims (households) as compensation. Received: December 1998/Accepted: May 2000     

争论-分析-评价：一种运用于战略规划的手段

赫尔辛基科技大学结合若干研究项目，开发了一种在规划过程中自始自终运用“争论-分析-评价”的方法。争论理论在许多研究领域得到普遍运用，特别是在20世纪50年代流行以来得到了更大的发展。虽然这种方法尚未经过实际规划过程的检验，但它已经被运用在规划文件的后期评价中。本文对这种方法的理论基础进行了阐述。     

Sequence-based detection of sleeping cell failures in mobile networks

This article presents an automatic malfunction detection framework based on data mining approach to analysis of network event sequences. The considered environment is long term evolution (LTE) of Universal Mobile Telecommunications System with sleeping cell caused by random access channel failure. Sleeping cell problem means unavailability of network service without triggered alarm. The proposed detection framework uses N-gram analysis for identification of abnormal behavior in sequences of network events. These events are collected with minimization of drive tests functionality standardized in LTE. Further processing applies dimensionality reduction, anomaly detection with K-Nearest Neighbors, cross-validation, postprocessing techniques and efficiency evaluation. Different anomaly detection approaches proposed in this paper are compared against each other with both classic data mining metrics, such as F-score and receiver operating characteristic curves, and a newly proposed heuristic approach. Achieved results demonstrate that the suggested method can be used in modern performance monitoring systems for reliable, timely and automatic detection of random access channel sleeping cells.     

Double-resonance SAW filters

A novel surface acoustic wave filter on a leaky-wave substrate is studied. It features a hiccup-type resonance occurring around a distributed gap between two long interdigital transducers. Compared to a classical coupled resonator filter, it enables a relatively narrow passband (1% to 2% of center frequency) with low insertion loss, steep skirts, and improved suppression levels. The structure consists of long transducers having the number of fingers greater than 1/K2 and 1/kappa where K2 is the coupling coefficient of the substrate material and kappa is the reflectivity per wavelength, separated with short transducer sections constituting a distributed gap. A strong, localized resonance is formed in the gap region, in addition to the resonance arising in the long structures-hence, the name double-resonance filter. The substrate studied here is 42 degrees-rotated lithium tantalite. We show experimental results for both single-ended and unbalanced-to-balanced filters at 1.6 GHz, having a minimum insertion loss of 1.07 dB, suppressions of 30 dB, and absolute -3-dB bandwidth of 29 MHz (1.9% of the center frequency). For the balanced device, the amplitude imbalance over the passband ranges from -0.6 dB to 2 dB and the phase imbalance from 1 degrees to 4.5 degrees. Furthermore, we have measured the acoustical power distributions using a scanning laser interferometer, and we compare these results with the profiles simulated using a coupling-of-modes model.     

Data generative machine learning model for the assessment of outdoor thermal and wind comfort in a northern urban environment

Predicting comfort levels in cities is challenging due to the many metric assessment. To overcome these challenges, much research is being done in the computing community to develop methods capable of generating outdoor comfort data. Machine Learning (ML) provides many opportunities to discover patterns in large datasets such as urban data. This paper proposes a data-driven approach to build a predictive and data-generative model to assess outdoor thermal comfort. The model benefits from the results of a study, which analyses Computational Fluid Dynamics (CFD) urban simulation to determine the thermal and wind comfort in Tallinn, Estonia. The ML model was built based on classification, and it uses an opaque ML model. The results were evaluated by applying different metrics and show us that the approach allows the implementation of a data-generative ML model to generate reliable data on outdoor comfort that can be used by urban stakeholders, planners, and researchers.