Terms Of Seconds Research Articles

A fully coupled thermo-poro-elastic model predicting the stability of wellbore in deep-sea drilling. Part A: Analytic solutions

Wellbore stability is important to deep-sea drilling (DSD) for exploiting offshore oil and gas resources. Accurate prediction of the mechanical behaviors of rock formation around the wellbore can effectively prevent wellbore failure via adjusting mud weight. In this paper, a fully coupled thermo-poro-elastic (THM) model is developed by combining fluid circulation in the wellbore and rock deformation in the reservoir. Transient heat transfer in the wellbore/reservoir and heat exchange between the tubing, annulus, riser, casing, cement, seawater and rock formation are considered. By decomposing the problem into axisymmetric and antisymmetric sub-problems, the analytical solutions for transient temperature, pressure and stress in the rock formation and fluid temperature changes in the drill pipe, annulus and seawater near the riser are obtained and validated against with the numerical solutions, existing fluid circulation model, field measurement data and the existing model without considering fluid circulation. After that, a typical case study is carried out to show the mechanical behavior around the wellbore. It is found that the proposed fully coupled THM model has a high accuracy with a relative error of around 1.2%. There is a large difference in the predicted bottomhole temperature (BHT) and thus the temperature in the reservoir between the models with and without considering fluid circulation in the wellbore. An assumption of constant temperature boundary condition may lead to overestimated or underestimated results depending on the selection of the assigned wellbore temperature. In the DSD case studied, the rock formation at the upper part of the reservoir (Z < 0.40) is continuously heated and the rock formation at the lower part (Z > 0.6) of the reservoir is continuously cooled during fluid circulation, which thus results in a complex heat transfer and thus mechanical behavior in the wellbore/reservoir system, especially near the wellbore. The bottomhole temperature (BHT) decreases by 38.9 K due to cold fluid circulation from 3.68 min to 25.68 days, which can lead to 14.59 MPa tensile stress that cannot be ignored for wellbore stability analysis. The proposed analytical model provides a useful tool to predict the mechanical behaviors such as the transient temperature, pressure, displacement and stresses in the wellbore/reservoir system during fluid circulation in DSD. It runs efficiently in terms of seconds per case study in a portable laptop computer and can also work a benchmark for other numerical methods. However, the fully coupled THM model and its analytical solution are based on several assumptions, such as the heat generated by the drill bit rotation is ignored and only the liquid phase is considered, which requires further investigation.

Shear Bond Strength, Bonding Time and Adhesive Remnant Index of Adhesive Precoated Flash Free Adhesive System vs Conventional Adhesive System using Metal Brackets: An In-vitro Study

Introduction: With advances in materials for bonding in orthodontics, errors regarding amount of adhesive to be used can be controlled. Adhesive Precoated (APC™) Brackets were introduced to reduce the step of applying conventional adhesive on base of the bracket. Moreover, APC™ Flash Free Adhesive System (FFAS) eliminated the step of removal of excessive adhesive around the brackets. Aim: To compare Shear Bond Strength (SBS), Bonding Time (BT) and Adhesive Remnant Index (ARI) between Conventional Adhesive System (CAS) and APC™ FFAS using metal brackets Materials and Methods: This in-vitro study was carried out in the Department of Orthodontics and Dentofacial Orthopaedics at Bharati Vidyapeeth (Deemed to be University) Dental College and Hospital, Sangli, Maharashtra, India. A total of 78 teeth with metal braces were split into two groups, with 39 samples each receiving treatment with the CAS and the APCTM FFAS. Shear bond forces were applied to each sample using a universal testing machine and recorded in Megapascals (MPa) to provide an indication of SBS. Both Groups’ BT was quantified in terms of seconds. The stereomicroscope indexes of Artun J and Bergland S were used to determine ARI. Microsoft Excel was used for data entry, while Statistical Package for Social Sciences (SPSS) version 24.0 was used for analysis. The normality of the data was tested using two different t-tests. In terms of mean and standard deviation, descriptive statistics were represented. A significant level of 0.05 was used. Results: SBS values were 10.35±3.55 MPa and 11.23±3.82 MPa in CAS and FFAS respectively. No significant difference was found among the two groups (p≤0.29) in SBS. BT was significantly (p≤0.001) less in FFAS (95.54±8.72 seconds) compared to CAS (140.85±16.62 seconds). ARI was significantly (p≤0.002) less in FFAS (1.79±0.80) in comparison with CAS (1.23±0.74). Conclusion: FFAS brackets perform better in comparison to CAS in case of BT and ARI. Both groups show no significant difference in SBS.

The aesthetics of isochrony and literal synchrony in voice-over translation

Voice-over translation is characterised by some technical synchronic features (isochrony, literal synchrony, action synchrony, kinetic synchrony, content synchrony and character synchrony). From these, isochrony and literal synchrony contribute to the illusion of authenticity and realism with what is called sound bites (a time span in the target version in which we only hear the original voice, and which can occur at the beginning and/or at the end of the speaker’s intervention). In our study, after analysing a corpus made up of different voiced-over programmes using speech analysis software and a spreadsheet, we have seen that the average duration of sound bites differs from that stated by the scholarly tradition both in terms of seconds and number of words. In addition, we also analysed samples that show no literal synchrony to see how and whether the rendition success of those parts could be affected. The results confirm that sound bites and literal synchrony are aesthetic enhancers which provide voice-over with an authenticity feel that makes it, for some scholars, the most faithful and reliable audiovisual translation mode.

Accurate Current Sharing and Voltage Regulation in Hybrid Wind/Solar Systems: An Adaptive Dynamic Programming Approach

Renewable energy is an advisable choice to reduce fuel consumption and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rm CO_{2}$ </tex-math></inline-formula> emission. Therein, wind energy and solar energy are the most promising contributors to reach this goal. Although the hybrid wind/solar system has been widely studied, the real-time current sharing based on their maximum capacities is rarely achieved in terms of seconds. Based on this, this paper proposes an accurate current sharing and voltage regulation approach in hybrid wind/solar systems, which is based on distributed adaptive dynamic programming approach. Firstly, the equivalent wind/solar model is built, which is an indispensable preprocessing to achieve the complementary between wind energy and solar energy. Therein, the wind energy and solar energy can output relative current according to their respective capacity ratio, which ensure the maximum utilization ratio of renewable energy source. Furthermore, current sharing and voltage regulation problem is switched into optimal control problem. Under this effect, each source agent aims to obtain the optimal control variable and achieve accurate current sharing/voltage regulation. Moreover, an adaptive dynamic programming approach based on Bellman principle is proposed. It can achieve accurate current sharing and voltage regulation. Finally, the simulation results are provided to illustrate the performance of the proposed adaptive dynamic programming approach.

An efficient model for predicting heat extraction from a multiple-well enhanced geothermal system in the presence of areal flow

To maximize the heat production from an enhanced geothermal system (EGS), multiple-well layouts have been proposed. In this paper, a semi-analytical model is developed for predicting heat extraction from a multiple-well system including injection and production wells, which are connected by a single planar aquifer with a constant thickness. By utilizing velocity potentials and streamline functions, analytical solutions for the temperature along streamlines in the Laplace space are obtained, followed by their numerical inversion to time-domain results. The model is verified through comparisons with existing results and those obtained by commercial package. Besides, the model is found to be very efficient in terms of seconds per run, compared to pure numerical models, in saving CPU time and providing acceptable results. After that, the thermal performance of eight different well layouts is compared to find the optimal well layout in terms of heat extraction for the EGS at Qiabuqia geothermal area in the Gonghe Basin, China. It is found that the magnitude and direction of the areal flow, and the well layout significantly influence the fluid flow and thermal behaviors. When the areal flow velocity is low (i.e. 10-5 m/s), the layout with 4 injection wells (IWs) and 5 production wells (PWs) exhibit the overall best output performance in terms of output thermal power (OTP) and total heat extracted (THE). However, if the areal flow velocity is high (i.e. 5 × 10-5 m/s), a dipole-well system, can maximize the OTP and THE if the two wells are placed parallel to the areal flow with the downstream IW and upstream PW.

Multiscale and monolithic arbitrary Lagrangian–Eulerian finite element method for a hemodynamic fluid-structure interaction problem involving aneurysms

In this paper, a multiscale and monolithic arbitrary Lagrangian–Eulerian finite element method (ALE-FEM) is developed for a multiscale hemodynamic fluid-structure interaction (FSI) problem involving an aortic aneurysm growth to quantitatively predict the long-term aneurysm risk in the cardiovascular environment, where the blood fluid profile, the hyperelastic arterial wall, and the aneurysm pathophysiology are integrated into one hemodynamic FSI model, together with no-slip interface conditions between the blood fluid and the arterial wall. Additionally, two different time scales are involved: a fast time scale for the blood fluid-arterial wall interaction process in terms of seconds, and a slow time scale for the biological (abdominal aortic aneurysms (AAA) progression) process in terms of years. Two types of multiscale methods, the heterogeneous multiscale method (HMM) and the seamless multiscale method (SMM), are employed to tackle different time scales while the arbitrary Lagrangian–Eulerian (ALE) method is adopted to generate the moving blood fluid meshes that adapt to the deformation of the hyperelastic arterial wall all the time, based on which the variable time-stepping/mixed finite element method (FEM) is defined in the ALE frame to discretize the developed hemodynamic FSI model involving aneurysms. A two-dimensional schematic blood fluid-artery-aneurysm interaction example and a three-dimensional realistic cardiovascular FSI problem with an aortic aneurysm growth based upon the patients' CT scan data are simulated to validate the accuracy and the efficiency of our developed HMM(SMM)/ALE-FEM, and a medically reasonable long-term prediction is obtained for the aneurysm growth as well.

Vascular reactivity of cutaneous circulation to brief compressive stimuli, in the human forearm.

A brief compressive stimulus is known to induce a rapid hyperemia in skeletal muscles, considered to contribute to the initial phase of functional hyperemia. Whether the same mechano-sensitivity characterizes the cutaneous circulation is debated. This study aims to investigate whether a rapid hyperemic response to compressive stimuli is also expressed by skin blood flow in humans. In 12 subjects, brief compressive stimuli were delivered to the forearm at varying pressures/durations (50/2, 100/2, 200/2, 200/1, 200/5mmHg/s); the sequence was randomized and repeated with the arm above and below heart level. Laser Doppler flowmetry technique was used to monitor skin blood flow. The response was described in terms of peak skin blood flow normalized to baseline (nSBFpeak), time-to-peak from the release of compression, and excess blood volume (EBV, expressed in terms of seconds of basal flow, s-bf) received during the response. The results consistently evidenced the occurrence of a compression-induced hyperemic response, with nSBFpeak = 2.9 ± 1.1, EBV = 17.0 ± 6.6s-bf, time-to-peak = 7.0 ± 0.7s (200mmHg, 2s, below heart level). Both nSBFpeak and EBV were significantly reduced (by about 50%) above compared to below heart level (p < 0.01). In addition, EBV slightly increased with increasing pressure (p < 0.05) and duration (p < 0.01) of the stimulus. For the first time, the rapid dilatator response to compressive stimuli was demonstrated in human cutaneous circulation. The functional meaning of this response remains to be elucidated.

Choquet integration by Simpson’s rule with application in Hellinger distance

In non-additive measure theory, there are a few studies on the numerical Choquet integral in continuous case on real line. Recently, based on the statistics software R, Torra and Narukawa (Inf Fusion 31:137–145, 2016) considered the problem of computing a numerical Choquet integral and some algorithms for Hellinger distance between two monotone measures. In this paper, the composite Simpson rule for numerical Choquet integration is proposed. Then some algorithms in Mathematica software are given. As well as, CPU time of the Examples in terms of seconds is reported which shows, in computational view, the presented method has a high speed.

A Parallel Multilevel Feature Selection algorithm for improved cancer classification

Biological data is prone to grow exponentially, which consumes more resources, time and manpower. Parallelization of algorithms could reduce overall execution time. There are two main challenges in parallelizing computational methods. (1) Biological data is multi-dimensional in nature. (2). Parallel algorithms reduce execution time, but with the penalty of reduced prediction accuracy. This research paper targets these two issues and proposes the following approaches. (1) Vertical partitioning of data along feature space and horizontal partitioning along samples in order to ease the task of data parallelism. (2) Parallel Multilevel Feature Selection (M-FS) algorithm to select optimal and important features for improved classification of cancer sub-types. The selected features are evaluated using parallel Random Forest on Spark, compared with previously reported results and also with the results of sequential execution of same algorithms. The proposed parallel M-FS algorithm was compared with existing parallel feature selection algorithms in terms of accuracy and execution time. The results reveal that parallel multilevel feature selection algorithm improved cancer classification resulting into prediction accuracy ranging from ∼85% to ∼99% with very high speed up in terms of seconds. On the other hand, existing sequential algorithms yielded prediction accuracy of ∼65% to ∼99% with execution time of more than 24 hours.

A De-Compositional Approach to Regular Expression Matching for Network Security

Regular Expression (RegEx) matching is the industry standard for Deep Packet Inspection (DPI) because RegExes are significantly more expressive than strings. To achieve high matching speed, we need to convert the RegExes to Deterministic Finite State Automata (DFA). However, DFA has the state explosion problem, that is, the number of DFA states and transitions can be exponential with the number of RegExes. Much work has addressed the DFA state explosion problem; however, none has met all the requirements of fast and automated construction, small memory image, and high matching speed. In this paper, we propose a decompositional approach, with fast and automated construction, small memory image, and high matching speed, to DFA state explosion. The first key idea is to decompose a complex RegEx that cause exponential state increases into a set of simpler RegExes that do not cause exponential state increases, where any character string that matches the complex RegEx also matches all the RegExes in the set of simpler RegExes; that is, the set of strings that match the complex RegEx is a subset of strings that match the set of simpler RegExes. The second key idea is to use a stateful post-processing engine to filter the matches that are actually the matches of the complex RegEx. Given an input string for matching, instead of using the large DFA constructed from the original complex RegEx to perform the matching, we first use the small DFA constructed from the set of simpler RegExes to perform the matching, and then, if the small DFA reports a match, we use the post-processing engine to determine whether it is a true match to the original complex RegEx. Because the pre-processing is simple, automaton construction can be automated and fast, and because most on-line processing is done by a DFA, its matching speed is close to that of a DFA alone. Our experimental results show that our decompositional approach achieves orders of magnitude faster DFA construction (in terms of seconds instead of minutes), 30 times smaller memory image, and 43% faster matching speeds, than state-of-the-art software based RegEx matching algorithms.

Cloud Brokering with Bundles: Multi-objective Optimization of Services Selection

Abstract Cloud computing has become one of the major computing paradigms. Not only the number of offered cloud services has grown exponentially but also many different providers compete and propose very similar services. This situation should eventually be beneficial for the customers, but considering that these services slightly differ functionally and non-functionally -wise (e.g., performance, reliability, security), consumers may be confused and unable to make an optimal choice. The emergence of cloud service brokers addresses these issues. A broker gathers information about services from providers and about the needs and requirements of the customers, with the final goal of finding the best match. In this paper, we formalize and study a novel problem that arises in the area of cloud brokering. In its simplest form, brokering is a trivial assignment problem, but in more complex and realistic cases this does not longer hold. The novelty of the presented problem lies in considering services which can be sold in bundles. Bundling is a common business practice, in which a set of services is sold together for the lower price than the sum of services’ prices that are included in it. This work introduces a multi-criteria optimization problem which could help customers to determine the best IT solutions according to several criteria. The Cloud Brokering with Bundles (CBB) models the different IT packages (or bundles) found on the market while minimizing (maximizing) different criteria. A proof of complexity is given for the single-objective case and experiments have been conducted with a special case of two criteria: the first one being the cost and the second is artificially generated. We also designed and developed a benchmark generator, which is based on real data gathered from 19 cloud providers. The problem is solved using an exact optimizer relying on a dichotomic search method. The results show that the dichotomic search can be successfully applied for small instances corresponding to typical cloud-brokering use cases and returns results in terms of seconds. For larger problem instances, solving times are not prohibitive, and solutions could be obtained for large, corporate clients in terms of minutes.

Using hierarchical statistical analysis and deep neural networks to detect covert timing channels

Covert timing channels provide a mechanism to leak data across different entities. Manipulating the timing between packet arrivals is a well-known example of such approach. The time based property makes the detection of the hidden messages impossible by traditional security protecting mechanisms such as proxies and firewalls. This paper introduces a new generic hierarchical-based model to detect covert timing channels. The detection process consists of the analysis of a set of statistical metrics at consecutive hierarchical levels of the inter-arrival times flows. The statistical metrics considered are: mean, median, standard deviation, entropy, Root of Average Mean Error (RAME). A real statistical metrics timing channel dataset of covert and overt channel instances is created. The generated dataset is set to be either flat where the statistical metrics are calculated on all flows of data or hierarchal (5 levels of hierarchy were considered) where the statistical metrics are computed on sub parts of the flow as well. Following this method, 5 different datasets were generated, and used to train/test a deep neural network based model. Performance results about accuracy and model training time showed that the hierarchical approach outperforms the flat one by 4 to 10 percent (in terms of accuracy) and was able to achieve short model training time (in terms of seconds). When compared to the Support Vector Machine (SVM) classifier, the deep neural network achieved a better accuracy level (about 2.3% to 12% depends on the used kernel) and significantly shorter model training time (few seconds versus few 100’s of seconds). This paper also explores the importance of the used metrics in each level of the detection process.

On the indeterminacy of the meter

In the International System of Units (SI), ‘meter’ is defined in terms of seconds and the speed of light, and ‘second’ is defined in terms of properties of cesium 133 atoms. I show that one consequence of these definitions is that: if there is a minimal length (e.g., Planck length), then the chances that ‘meter’ is completely determinate are only 1 in 21,413,747. Moreover, we have good reason to believe that there is a minimal length. Thus, it is highly probable that ‘meter’ is indeterminate. If the meter is indeterminate, then any unit in the SI system that is defined in terms of the meter is indeterminate as well. This problem affects most of the familiar derived units in SI. As such, it is highly likely that indeterminacy pervades the SI system. The indeterminacy of the meter is compared and contrasted with emerging literature on indeterminacy in measurement locutions (as in Eran Tal’s recent argument that measurement units are vague in certain ways). Moreover, the indeterminacy of the meter has ramifications for the metaphysics of measurement (e.g., problems for widespread assumptions about the nature of conventionality, as in Theodore Sider’s Writing the Book of the World) and the semantics of measurement locutions (e.g., undermining the received view that measurement phrases are absolutely precise as in Christopher Kennedy’s and Louise McNally’s semantics for gradable adjectives). Finally, it is shown how to redefine ‘meter’ and ‘second’ to completely avoid the indeterminacy.

Closure to discussion on "A method for short-term wind power prediction with multiple observation points"

Summary form only given. The authors appreciate the valuable comments expressed by the discussers. Our comments are numbered to match the points made in the discussions. 1) It is true that time frames for wind power forecasting are very important for different applications. For example, very short-term wind power forecasting, in terms of seconds to minutes, is important for frequency control, electricity market clearing, and regulation actions. Short-term wind power forecasting, in terms of minutes to hours, is used for economic load dispatch planning and load increment/decrement decisions. Similarly, long-term wind power forecasting, in terms of hours to days, is required for other applications like unit commitment, maintenance scheduling to obtain optimal operating cost, reserve requirement decisions, prediction of power system congestion, and operational security in day-ahead electricity market. In particular, short-term wind power predictions are becoming increasingly important nowadays since the rise of the competitive electricity markets. In this paper, initially the authors have tested the algorithm only for some minutes ahead. However, the prediction for other time frames would be considered in the future. 2) As mentioned in the paper, the optimum values of the model parameters were found by numerical iterations. While making the empirical studies, it was observed that historical time interval during each exercise was different for different data ranges and times. Therefore, the optimal number of historical data points for the given data set was chosen based on manual trial-and-error methods. 3) First of all, we thank the discussers for their appreciation for the proposed idea. The accuracy improvement for wind power prediction was calculated by comparing the results of direction-dependent power curves with a single average power curve for the given data set. It depends on wind velocity as the discusser mentioned. As regards the correlation between the spread of data in Fig. 7 and the spread of data due to wind direction, actually Fig. 7 is shown as a general example to compare a manufacturer's power curve, as in Fig 6, and an actual power curve in a wind farm. In particular, unfortunately it is not the plot of same actual data used in the analyses. Therefore, specifically there is no relation of Fig. 7 with our direction-dependent power curves. As our analyses are based on numerical calculations, we have not worked out analytical relation yet to describe the wind power relation with wind speed and direction together. However, based on these preliminary results and discussers' comments, we will improve this idea of direction-dependent power curves with a generalized relation and conclusion. 4) The wind direction was not predicted using Persistence and Grey model. The proposed method has not been compared to other neural networks or Bayesian-based methods yet. We would consider to improve the proposed technique with automatic and adaptive tuning of the model parameters along with its comparison with other advanced prediction techniques. Once again, we are thankful to the discussers for their interest in our research paper and valuable feedback.

Isolation, characterization and expression profile of Cistus creticus ssp. creticus genes involved in terpenoid biosynthesis

S15 tic changes in both transcriptional levels of many genes and as well as in intracellular and extracellular metabolite levels. The dynamic response of the yeast cells fell either into short time series responses, measured in terms of seconds, or they could be observed as a longer time series response, measured in minutes, or in some cases, hours. With the integration of the dynamic transcriptome and metabolome data, we aim to achieve a more thorough understanding of the yeast as a whole.

A technique for measuring CO 2 and water vapor profiles within and above plant canopies over short periods

A multiport air sampling apparatus was developed to measure vertical profiles of CO 2 and water vapor concentrations within and above the plant canopy over time intervals of as short as 5 min. Air is drawn continuously from six heights through tubings of equal length and diameter, each connected to a three-way solenoid valve. Flow through five of the six intake lines is driven by a large purge pump while the air from the selected sampling height is drawn by a small sample pump and pushed through an infrared gas analyzer (IRGA) for the simultaneous measurements of CO 2 and water vapor concentrations. A data logger controls the solenoid valves and switches the air from each height sequentially through the IRGA. The internal volume of the apparatus is minimized to ensure a fast response in IRGA output when the sample air switches from one height to another. The response was shown to be essentially complete within 2 s or less. By delaying signal recording for 2 s after switching, one cycle of sequential measurements over the six heights is completed in 1 min, and 5 min mean profiles are obtained as the mean of five 8 s measurement periods spaced 1 min apart for each height. The short interval between each measurement period is essential when the scalar concentrations fluctuate or change rapidly. We compared the water vapor pressure within the upper part of a cotton canopy measured with our apparatus, with that measured by a precision, shielded and ventilated psychrometer made of platinum resistance thermometers. The results showed excellent agreement over the daily cycle between the two instruments for the 30-min mean data, and very good agreement for the 5-min mean data, showing coincidence of nearly all the 5-min peaks and troughs between the two methods. Sample diurnal patterns measured by the apparatus over a maize field spanning two consecutive days with contrasting wind speeds are given. The delay of nearly 2 s in response is mostly due to the internal volume of the apparatus. Taking the time required to clear this volume upon switching to a new port into account, it is possible to make CO 2 measurements of slightly reduced accuracy at a rate of 1 s per port. The potential use of the apparatus for measuring at several heights over very short time intervals (in terms of seconds) is discussed in the context of the requirements for studying coherent turbulence structures and calculating the storage term in CO 2 flux determinations.

ChemSkill Builder, Version 5.1 (Spain, James D.; Peters, Harold J.)

James D. Spain and Harold J. Peters. Electronic Homework Systems, Inc.: 129 Leslie Lane, Pendleton, SC, 1997. ISBN 29670-9697. $19.50The day of electronic homework in general chemistry classes is rapidly approaching and, indeed, has arrived for many chemistry instructors. It is difficult to fully understand all the possibilities available, but the ChemSkill Builder should be considered by all criteria to be one of the best General Chemistry electronic homework packages.The package is a 3-disk set or a CD plus a record management disk. The program is divided into 24 chapters much like the topics of nearly all general chemistry textbooks. Each chapter is usually subdivided into four to six subsections. Each subsection contains instruction and a set of questions. Since the number of questions varies and the actual questions differ each time a student goes through the subunit, each student has a unique set of questions.Students can repeat subunits or entire chapters; their highest score will be recorded. The time spent on each subunit is also recorded. The scores can easily be downloaded to an electronic spreadsheet, gradebook, etc.The questions in this program range in difficulty. If one is not answered correctly, the computer offers helpful hints, and after two unsuccessful attempts the correct answer is given. The programs will not move to the next question until a question has been answered correctly or two wrong attempts have been entered. Partial credit is given when the correct answer is given on a second attempt. Especially during the first several chapters, the use of significant figures and the inclusion of units are strictly enforced.The program was found to be friendly. It is easy to use, has large visuals, gives friendly comments, is patient, and gives immediate feedback, and the information is very well encrypted. To our knowledge our students have not been successful in attempts to falsify data, etc. Most attempts yielded a program that no longer worked.Each of the 24 units contains sufficient introductory comments and examples that the unit can stand alone. As a result, students can be assigned to work units in a variety of sequences. For example, our students study thermodynamics before equilibrium.ChemSkill Builder contains only minimal graphics, pop-up tables, and animation. The graphics are simple but one needs to remember that this programs fits on just 3 disks and sells for only about $20.The program is not without its faults. For example, the response of "okay" for a correct answer implies that a better answer was possible when no better answer was possible. There is an occasional annoying ding. There are some rather picky answers. For example, for the question "Is methane more or less volatile than methanol?" CSB would give credit for "more" but no credit for "more volatile". In the unit on kinetics the units for rate were not always given and students were left to guess whether the given rate is in terms of seconds or minutes. The treatment of the electron configuration of elements in the lanthanide series, the required space between terms in equilibrium expressions, and units in yrs but not yr or years are some of the other annoyances that I observed.Our students often comment about the many hours that they spend on their ChemSkill Builder assignments, but they also really believe that it is a very important learning aid. Even with its imperfections, limitations, lack of coordination with the textbook being used, and nit picking regarding significant figures and units, this is still an excellent program for the price. It does not write tests, print homework assignments, or tutor much beyond basic introduction to each unit; it simply does a commendable job of walking students through homework exercises and maintaining a record of the their efforts.The authors encourage interested individuals to check out the Web page at http://www.avalon.net/~Chemskill.

Timestamp semantics and representation

Many database management systems and operating systems provide support for time values. At the physical level time values are known as timestamps. A timestamp has a physical realization and a temporal interpretation. The physical realization is a pattern of bits while the temporal interpretation is the meaning of each bit pattern, that is, the time each pattern represents. All previous proposals defined timestamps in terms of seconds. However, as we show, there are at least seven definitions of this fundamental time unit. We propose a more precise temporal interpretation, the time-line clock, that constructs a time-line by using different well-defined clocks in different periods. We also propose timestamp formats for events, intervals and spans. These formats can represent all of time to the granularity of a second, and all of recorded history to a finer granularity of a microsecond. Our proposed formats were designed to be more space and time efficient than existing representations. We compare our formats with those used in common operating systems and database management systems.

An evaluation of the span and direction of spread of the concept "now" (Japanese ima): using both the dual scaling and factor analysis methods

The purpose of this study was to obtain information about both the span and direction of spread of the concept "now" (Japanese ima) used in short sentences such as "I am--a student." 583 subjects were presented with 55 sentences, and were required first to rate on a 5-point scale the degree of spread of the concept used in each sentence, and then to express its span and direction in terms of seconds, minutes, ... years, decades, or centuries in both a past- and a future-orientation. The latter data were analysed using the Dual Scaling method which revealed three major solutions: "span", "direction", and "interrelation between the previous two". The former data were analysed using the Factor Analysis method which revealed six factors: "moment", "conversion", "limitlessness", "absorption", "limitation" and "hopelessness". Furthermore, second-order analyses were carried out using these six factors, revealing three further factors: "duration", "change" and "timelessness". It was concluded that these latter three factors were identical with the three solutions obtained by Dual Scaling.

Colony Defence of two Honeybee Types and their Hybrid 1. Naturally Mated Queens

SummaryHoneybee colonies of Africanized and European (Italian) types, and hybrids between the two (Italian × Africanized), were assayed for eleven measures of colony defensive behaviour. The Africanized colonies were significantly more defensive than the European ones. The hybrids were intermediate to the parental types in terms of seconds to respond to a sting target, total stings delivered, number of bees around the colony entrance prior to testing (0 s), and number of bees in the air at 60 s and 90 s. The hybrids were similar to the European parent in terms of seconds to respond to alarm pheromone, number of responding bees around the colony entrance at 30 s, 60 s and 90 s, and the number of bees in the air at 0 s and 30 s.