Approximability of Clausal Constraints

We study a family of problems, called Maximum Solution (Max Sol), where the objective is to maximise a linear goal function over the feasible integer assignments to a set of variables subject to a set of constraints. When the domain is Boolean (i.e. restricted to {0,1}), the maximum solution problem is identical to the well-studied Max Ones problem, and the complexity and approximability is completely understood for all restrictions on the underlying constraints. We continue this line of research by considering the Max Sol problem for relations defined by regular signed logic over finite subsets of the natural numbers; the complexity of the corresponding decision problem has recently been classified by Creignou et al. (Theory Comput. Syst. 42(2):239–255, 2008). We give sufficient conditions for when such problems are polynomial-time solvable and we prove that they are APX-hard otherwise. Similar dichotomies are also obtained for variants of the Max Sol problem.     

Induction and Synchronous Motors Compared for System Stability

A comparison is made between synchronous motors and induction motors with regard to industrial power system stability. Representation of motor loads in stability studies is reviewed. The specific system studied is an infinite bus supplying a combination induction and synchronous motor load through a transmission line and transformer. The system is subjected to a fault at the transformer and critical values of fault clearing time are computer calculated for ratios of synchronous motor load to induction motor load from zero to unity. The effect of variation of motor parameters on clearing times is discussed.     

Schrifttumsberichte

Ohne Zusammenfassung     

Schrifttumsberichte

Ohne Zusammenfassung     

Energy cost and error performance of range-aware, anchor-free localization algorithms

Many applications that use sensor data from a wireless sensor network (WSN) require corresponding node position information as well. Therefore, it is not surprising that a common figure of merit for localization algorithms is the accuracy of the position estimate produced. Similarly, the amount of communication required by a localization algorithm is often of paramount interest as well since it is common knowledge that communication expends the most energy in a WSN. However, localization algorithms seldom characterize their communication cost. Furthermore, when they do it is often merely qualitative and is typically described as “expensive”. For two types of range-aware, anchor-free localization algorithms we found the opposite to be true. Rather than being expensive, the communication costs were quite modest. So much so that we maintain range-aware, anchor-free localization algorithms should be chosen on the basis of the accuracy required by the intended application independent of the communication cost.In this paper, we examine the effect of node degree, node distribution, range error and network size on distance error and communication cost for both incremental and concurrent versions of range-aware, anchor-free algorithms. The concurrent algorithm is twice as accurate as the incremental, but less efficient. Furthermore, node degree influences the energy cost of the algorithms the most, but neither algorithm uses more than a surprisingly small 0.8% of a 560 mA h battery. This result indicates less energy efficient localization algorithms can be tolerated, especially if they provide better accuracy. Furthermore, if energy does need to be conserved, there is not much savings available within the localization algorithm and savings must be found in other areas such as the MAC protocol or routing algorithm.     

Spektroskopische Untersuchungen an organischen Carbonylverbindungen. VI. NMR-Studien an substituierten β-Diketonen und ihren vinylogen Derivaten

Spectroscopic Investigations on Organic Carbonyl Compounds. VI. N.M.R.-Studies on Substituted β;-Diketones and their Vinyloge Derivatives . ¹³C- and ¹H-n.m.r.-data of substituted β-diketones and their vinyloge derivatives are presented. Most of the compounds exist chiefly in the enol-form. Only in the case of 4-dimethyl-aminodibenzoylmethane a keto-enol-equilibrium is registered. The influence of the substituent A and the chainlength on the position of the enol proton is discussed.     

Vibronic spectral behaviour of molecules. XV. Study on the T1 → S0 Phosphorescence of Isomeric Terphenyls

Underlying the completely-optimized S₀ and T₁ molecular geometries of isomeric terphenyls the corresponding theoretical vibronic T₁ → S₀ ‘line’ spectra calculated within the CONDON approach, are presented and compared with the experimental phosphorescences. The influence of possible conformations on the vibronic spectral behaviour is studied theoretically. The DUSHINSKY effect is found to be most important to the T₁ → S₀ phosphorescence of m-terphenyl. An analysis of the spectroscopically relevant vibrational modes is given.     

Health assessment of artisanal gold miners in Indonesia

Small scale miners use mercury to extract gold from ore in many countries. An environmental and health assessment was performed in Indonesia in two regions, Galangan in Central Kalimantan and Talawaan in Northern Sulawesi. The environmental assessment showed severe mercury contamination of the sediments, and increased mercury levels in local fish. For the health investigation 281 volunteers were recruited and examined by a standardized questionnaire, a neurological examination and neuro-psychological tests. A medical score was used consisting of significant factors of mercury intoxication. Mercury exposed workers showed typical symptoms of mercury intoxication, such as movement disorders (ataxia, tremor, dysdiadochokinesia, etc.). Blood, urine and hair samples were taken from any participant and analyzed for mercury. The mercury concentration in the biomonitors was high, partly extreme high in the working population, increased in the population living in the same habitat and low in the control group. By a standard protocol which includes a combination of threshold values of mercury in the biomonitors and a medical sum score the diagnosis of chronic mercury intoxication was made for highly burdened workers (amalgam smelters) in 55% in Sulawesi and in 62% in Kalimantan. Less exposed mineral processors and the general population in the mining areas were also intoxicated to a high percentage.     

Spektroskopie und Photochemie indigoider Verbindungen. V. Quantenchemische Berechnungen zum unterschiedlichen UV/S-Spektralverhalten der trans- und cis-Isomeren thioindigoider Verbindungen

Spectroscopy and Photochemistry of Indigoid Compounds. V. Quantum Chemical Calculations on the Different UV/VIS Spectral Behaviour of trans- and cis-Isomers of Thioindigoid Compounds The concept of non-bonding S…O-interaction [3] has been proved for some thioindigoid compounds. The different spectral behaviour of trans- and cis-isomers with regard to the long wave absorption band is mainly dependent on the number of S…O-structural units and on the S…O-distance. As compared to a coplanar structure twisting about the central double bond can result both in an increasing and a decreasing spectral shift.