Commenced in January 2007
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Edition: International
Paper Count: 237

Search results for: pubertal timing

237 Objectifying Media and Preadolescents' Media Internalization: A Developmental Perspective

Authors: Ann Rousseau, Steven Eggermont


The current study sought to explain pre-adolescents’ differential susceptibility to the internalization of mediated appearance ideals, using a three-wave panel survey of preadolescent girls and boys (N = 973, Mage = 11.14). Based on the premises of objectification theory and sexual script theory, we proposed a double role for pubertal timing and cross-sex interactions in preadolescents’ media internalization. More specifically, we expected pubertal timing and cross-sex interactions to (a) trigger higher levels of media internalization, directly and indirectly via body surveillance, and (b) positively moderate the relationship between objectifying media exposure and girls’ and boys’ media internalization. A first cross-lagged model tested whether the pubertal timing and cross-sex interactions could trigger preadolescents media internalization and body surveillance. Structural equation analysis indicated that pubertal timing (Wave1) positively predicted body surveillance and media internalization (both Wave3). Cross-sex involvement (Wave1) was positively linked to media internalization (Wave2), but body surveillance (Wave2) was not associated with cross-sex interactions. Results also showed a reciprocal interaction between media internalization (Wave 2 and 3) and body surveillance (Wave2 and 3). Multiple group analysis showed that the observed relationships did not vary by gender. A second moderated moderation model examined whether (a) the relationship between objectifying media exposure (television and magazines, both Wave1) and media internalization (Wave3) depended on pubertal timing (Wave1), and (b) the two-way interaction between objectifying media exposure (Wave1) and pubertal timing (Wave1) varied depending on cross-sex interactions (Wave1). Results revealed that cross-sex interactions functioned as a buffer against media internalization. For preadolescents who had fewer cross-sex interactions, early puberty (relative to peers) positively moderated the relationship between magazine exposure and the internalization of mediated appearance ideals. No significant relationships were found for television. Again, no gender difference could be observed. The present study suggests a double role for pubertal timing and cross-sex interactions in preadolescents media internalization, and indicate that early developers with few cross-sex experiences are particularly vulnerable for media internalization. Additionally, the current findings suggest that there is relative gender equity in magazines’ ability to cultivate media internalization among preadolescents.

Keywords: cross-sex interactions, media effects, objectification theory, pubertal timing

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236 Pubertal Development among 10-Year-Olds: The Role of Parent's Attachment Style

Authors: Hanit Ohana, Anat Scher


For decades, attachment research examined how mothers’ attachment styles shape parenting and specific aspects of child development. Only limited research addressed pubertal development from the perspective of attachment relationships. The current study focused on pubertal development at 10 years of age, as defined by Tanner (PDS), and examined the associations with both mothers’ and fathers’ attachment styles (ECR-S). Sixty-nine parents and their children from a medium SES participated in the study. It was found that whereas mothers’ attachment was not related to the child’s puberty development, fathers’ attachment was associated with their daughter’s pubertal development. Specifically, in girls, but not boys, advanced pubertal development was positively correlated with fathers’ avoidance (r = .37, p = 0.05), and negatively correlated with anxiety scores (r = -.36, p = 0.05). This result raises the possibility that for girls, a relationship with fathers may serve as a psychological stressor, and in turn, induce concerns regarding resources and availability of interpersonal support. Such processes may contribute to different reproductive timing and strategies, including delayed and accelerated pubertal development. As more data are collected, we will be able to address with more power the role of parent’s attachment in shaping the pubertal development of their young adolescents. Expanding the understanding of aspects of pubertal development –an important milestone of human development- and the possible linkages with parental attachment is important for researchers and clinicians.

Keywords: attachment style, children, gender, parents, puberty

Procedia PDF Downloads 58
235 Impact of Nutritional Status on the Pubertal Transition in a Sample of Egyptian School Girls

Authors: Nayera E. Hassan, Salah Mostafa, Hamed Elkhayat, Kalled Hassan Sewidan, Sahar A. El-Masry, Manal Mouhamed Ali, Mones M. Abu Shady


Pubertal growth is influenced by many factors including environmental and nutritional factors. Objective: To assess impact of nutritional status on pubertal staging, ovarian and uterine volumes among school girls. Method: Study was cross sectional and carried out on 1000 healthy school girls, aged 8-18 years selected randomly. They were categorized according to their ages into three groups: 8-12 years, 13-15 years and 16-18 years ±6 months, then according to their body mass index percentile to normal weight: (≥15-<85.), overweight (≥85-<95) and obese (≥95). All girls were subjected for physical, anthropometric (weight, height, body mass index), nutritional markers WAZ (weight/age Z score), HAZ (height/age Z score) and BMI-Z (body mass index Z score), pubertal assessment (Tanner stage) and pelvic transabdominal sonography (uterine and ovarian volumes). Results: Highly significant differences in ovarian and uterine volumes and nutritional markers (WAZ, HAZ and BMI-Z score) were detected among different grades of puberty in the two age groups (8-12 years, 13-15 years) coming in advance of obese girls (with increase of BMI); except HAZ in the second age group. Girls aged 16-18 years reached to final volume for the uterus and ovary with insignificant differences. Pubertal stage, ovarian and uterine sizes were highly significantly correlated with nutritional markers. Mean ages of onset: of puberty, menarche and complete puberty were, 11.65 + 1.84, 14.79 + 1.75 and 15.02 + 1.68 years respectively. Conclusion: Nutritional status has a crucial role in determining pubertal stage, ovarian and uterine volumes among Egyptian girls during the pubertal process.

Keywords: pubertal stage, nutritional markers, girls, ovarian and uterine volumes

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234 Do European Hedge Fund Managers Time Market Liquidity?

Authors: Soumaya Ben Kheilifa, Dorra Mezzez Hmaied


We propose two approaches to examine whether European hedge fund managers can time market liquidity. Using a sample of 1616 European hedge funds, we find evidence of liquidity timing. More importantly, this ability adds economic value to investors. Thus, it represents valuable managerial skill and a major source of European hedge funds’ performance. Also we show that the majority of these funds demonstrate liquidity timing ability especially during liquidity crisis. Finally, it emerged that our main evidence of liquidity timing remains significant after controlling for market timing and volatility timing.

Keywords: european hedge funds, liquidity timing ability, market liquidity, crisis

Procedia PDF Downloads 299
233 Libido and Semen Quality Characteristics of Post-Pubertal Rabbit Bucks Fed Ginger Rhizome Meal Based Diets

Authors: I. P. Ogbuewu, I. F. Etuk, V. U. Odoemelam, I. C. Okoli, M. U. Iloeje


The effect of dietary ginger rhizome meal on libido and semen characteristics of post-pubertal rabbit bucks was investigated in an experiment that lasted for 12 weeks. Thirty-six post-pubertal bucks were randomly assigned to 4 dietary groups of 9 rabbits each in a completely randomized design. Four experimental diets were formulated to contain ginger rhizome meal at 0 g/kg feed (BT0), 5g/kg feed (BT5), 10 g/kg feed (BT10), and 15g/kg feed (BT15) were fed ad libitum to the experimental animals. Results revealed that semen colour changed from cream milky to milky. Data on semen pH and sperm concentration were similar (p>0.05) among the dietary groups. Semen volume for the bucks in BT0 (0.64 mL) and BT5 (0.60 mL) groups were significantly (p<0.05) higher than those in BT10 (0.44 mL) and BT15 (0.46 mL) groups. Total spermatozoa concentration value was significantly (p<0.05) higher in BT0 and BT5 groups than those in BT10 and BT15 groups. Sperm motility and percent live sperm declined (p<0.05) progressively among the treatment groups. Percent dead sperm were significantly (p<0.05) lower for bucks in BT0 group than in BT10 and BT15 groups. Reaction time had a dose-dependent increase; however, the observed difference was not significant (p>0.05). These results indicate that the inclusion of ginger rhizome meal at 5-15g per kg feed in ration for post-pubertal rabbit bucks could cause mild depressive effect on semen production and quality.

Keywords: rabbits, semen, libido, ginger

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232 A Survey on Countermeasures of Cache-Timing Attack on AES Systems

Authors: Settana M. Abdulh, Naila A. Sadalla, Yaseen H. Taha, Howaida Elshoush


Side channel attacks are based on side channel information, which is information that is leaked from encryption systems. This includes timing information, power consumption as well as electromagnetic or even sound leaking which can exploited by an attacker. Implementing side channel attacks are possible if and only if an attacker has access to a cryptosystem. In this case, the attacker can exploit bad implementation in software or hardware which is not controlled by encryption implementer. Thus, he/she will represent a real threat to the security system. Several countermeasures have been proposed to eliminate side channel information vulnerability.Cache timing attack is a special type of side channel attack. Here, timing information is collected and analyzed by an attacker to guess sensitive information such as encryption key or plaintext. This paper reviews the technique applied in this attack and surveys the countermeasures against it, evaluating the feasibility and usability of each. Based on this evaluation, finally we pose several recommendations about using these countermeasures.

Keywords: AES algorithm, side channel attack, cache timing attack, cache timing countermeasure

Procedia PDF Downloads 200
231 Timing Equation for Capturing Satellite Thermal Images

Authors: Toufic Abd El-Latif Sadek


The Asphalt object represents the asphalted areas, like roads. The best original data of thermal images occurred at a specific time during the days of the year, by preventing the gaps in times which give the close and same brightness from different objects, using seven sample objects, asphalt, concrete, metal, rock, dry soil, vegetation, and water. It has been found in this study a general timing equation for capturing satellite thermal images at different locations, depends on a fixed time the sunrise and sunset; Capture Time= Tcap =(TM*TSR) ±TS.

Keywords: asphalt, satellite, thermal images, timing equation

Procedia PDF Downloads 248
230 A New IFO Estimation Scheme for Orthogonal Frequency Division Multiplexing Systems

Authors: Keunhong Chae, Seokho Yoon


We address a new integer frequency offset (IFO) estimation scheme with an aid of a pilot for orthogonal frequency division multiplexing systems. After correlating each continual pilot with a predetermined scattered pilot, the correlation value is again correlated to alleviate the influence of the timing offset. From numerical results, it is demonstrated that the influence of the timing offset on the IFO estimation is significantly decreased.

Keywords: estimation, integer frequency offset, OFDM, timing offset

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229 Timing and Noise Data Mining Algorithm and Software Tool in Very Large Scale Integration (VLSI) Design

Authors: Qing K. Zhu


Very Large Scale Integration (VLSI) design becomes very complex due to the continuous integration of millions of gates in one chip based on Moore’s law. Designers have encountered numerous report files during design iterations using timing and noise analysis tools. This paper presented our work using data mining techniques combined with HTML tables to extract and represent critical timing/noise data. When we apply this data-mining tool in real applications, the running speed is important. The software employs table look-up techniques in the programming for the reasonable running speed based on performance testing results. We added several advanced features for the application in one industry chip design.

Keywords: VLSI design, data mining, big data, HTML forms, web, VLSI, EDA, timing, noise

Procedia PDF Downloads 176
228 Best Timing for Capturing Satellite Thermal Images, Asphalt, and Concrete Objects

Authors: Toufic Abd El-Latif Sadek


The asphalt object represents the asphalted areas like roads, and the concrete object represents the concrete areas like concrete buildings. The efficient extraction of asphalt and concrete objects from one satellite thermal image occurred at a specific time, by preventing the gaps in times which give the close and same brightness values between asphalt and concrete, and among other objects. So that to achieve efficient extraction and then better analysis. Seven sample objects were used un this study, asphalt, concrete, metal, rock, dry soil, vegetation, and water. It has been found that, the best timing for capturing satellite thermal images to extract the two objects asphalt and concrete from one satellite thermal image, saving time and money, occurred at a specific time in different months. A table is deduced shows the optimal timing for capturing satellite thermal images to extract effectively these two objects.

Keywords: asphalt, concrete, satellite thermal images, timing

Procedia PDF Downloads 229
227 Factors for Entry Timing Choices Using Principal Axis Factorial Analysis and Logistic Regression Model

Authors: C. M. Mat Isa, H. Mohd Saman, S. R. Mohd Nasir, A. Jaapar


International market expansion involves a strategic process of market entry decision through which a firm expands its operation from domestic to the international domain. Hence, entry timing choices require the needs to balance the early entry risks and the problems in losing opportunities as a result of late entry into a new market. Questionnaire surveys administered to 115 Malaysian construction firms operating in 51 countries worldwide have resulted in 39.1 percent response rate. Factor analysis was used to determine the most significant factors affecting entry timing choices of the firms to penetrate the international market. A logistic regression analysis used to examine the firms’ entry timing choices, indicates that the model has correctly classified 89.5 per cent of cases as late movers. The findings reveal that the most significant factor influencing the construction firms’ choices as late movers was the firm factor related to the firm’s international experience, resources, competencies and financing capacity. The study also offers valuable information to construction firms with intention to internationalize their businesses.

Keywords: factors, early movers, entry timing choices, late movers, logistic regression model, principal axis factorial analysis, Malaysian construction firms

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226 A Golay Pair Based Synchronization Algorithm for Distributed Multiple-Input Multiple-Output System

Authors: Weizhi Zhong, Xiaoyi Lu, Lei Xu


In order to solve the problem of inaccurate synchronization for distributed multiple-input multiple-output (MIMO) system in multipath environment, a golay pair aided timing synchronization method is proposed in this paper. A new synchronous training sequence based on golay pair is designed. By utilizing the aperiodic auto-correlation complementary property of the new training sequence, the fine timing point is obtained at the receiver. Simulation results show that, compared with the tradition timing synchronization approaches, the proposed algorithm can provide high accuracy in synchronization, especially under multipath condition.

Keywords: distributed MIMO system, golay pair, multipath, synchronization

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225 A Second Spark Ignition Timing for the High Power Aircraft Radial Engine Using a CFD Transient Modeling

Authors: Tytus Tulwin, Adam Majczak


In aviation most important systems that impact the aircraft flight safety are duplicated. The ASz-62IR aircraft radial engine consists of two spark plugs powered by two separate magnetos. The relative difference in spark timing has an influence on the combustion process. The retardation of the second spark relative to the first spark was analyzed. The CFD simulation was developed as a multicycle transient model. Two independent spark sources imitate two flame fronts after an ignition period. It makes the combustion process shorter but only for certain range of second spark retardation. The model was validated by the in-cylinder pressure comparison. Combustion parameters were analyzed for different second spark retardation values. It was found that the most advantageous ignition timing in means of performance is simultaneous ignition. Nevertheless, for this engine the ignition time of the second spark plug is greatly retarded eliminating the advantageous performance influence. The reason behind this is maintaining high ignition certainty for all engine running conditions and for whole operating rpm range. In aviation the engine reliability is more important than its performance. Introducing electronic ignition system can yield from simultaneous ignition timing by increasing the engine performance and providing good reliability for all flight conditions. This work has been financed by the Polish National Centre for Research and Development, INNOLOT, under Grant Agreement No. INNOLOT/I/1/NCBR/2013.

Keywords: CFD, combustion, ignition, simulation, timing

Procedia PDF Downloads 219
224 Haematology and Reproductive Performance of Pubertal Rabbit Do Administer Crude Moringa oleifera (LAM.) Leaf Extract

Authors: Ewuola E. O., Sokunbi O. A., Oyedemi O. M., Sanni K. M


Moringa oleifera leaf has been traditionally used in the local medicine as an ingredient in some herbal formulations for blood purifier, cholesterol reducing agent, immune and reproductive enhancers. Twenty-four pubertal rabbit are divided equally into four groups were administered with varied concentrations of crude extract of the leaves of Moringa oleifera gavage at doses of 2.5ml/kg body weight (BW) in every 48 hours for 63 days. These rabbits were allotted into four treatments and each treatment was replicated six times to investigate the effect of administered crude Moringa oleifera leaf extract (CMOLE) on haematology and reproductive performance of pubertal rabbit does. Four experimental treatments were used. The animals on the control (T1) were administered water only. Rabbits on treatments 2, 3, and 4 were administered 100ml CMOLE/L, 200ml CMOLE/L, and 300ml CMOLE/L, respectively. The does were placed on extract two weeks before mating, five weeks after mating and continued for another two weeks after kindling. Six proven untreated bucks were used for the mating of the twenty-four treated does and these bucks were randomly allotted to the does such that each buck mated at least one treated does in each treatment. The same management practices and experimental diets were given ad libitum to all animals. Blood was sampled from the gestating does at the third trimester for haematological analysis. The haematology results showed that treated rabbits with 100ml CMOLE/L with mean corpuscular volume value of 93.38fl significantly (p < 0.05) higher than those on the control which is water only (82.24fl) but not significantly different from T3 (200ml CMOLE/L) and T4 (300ml CMOLE/L) which had mean values of 91.69fl and 91.49fl, respectively. While the erythrocyte counts, leukocyte counts, haematocrit, haemoglobin concentration, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentration, lymphocyte, neutrophil, monocyte, and eosinophil count were not significantly different across the treatments. For platelets, treated animals on T2 (100ml CMOLE/L) had the highest numerical value of 148.80 x 109/L which was identical with those on T3 (200ml CMOLE/L) with mean value of 141.50x109/L but significantly (p < 0.05) higher than those on T4 (300ml CMOLE/L) with mean value of 135.00 x 109/L and those on the control which had the least mean value of 126.60 x 109/L. The percentage conception rate of the treated animals was higher than those in the control group. The animals administered 300ml CMOLE/L had the apparently highest litter size of 5.75, while gestation length and litter weight tended to decline with increase in CMOLE concentrations The investigation demonstrated the potential effect of crude Moringa oleifera leaf extract on pubertal rabbit does. The administration of up to 300ml crude Moringa oleifera leaf extract per liter did not adversely affect but improved the haematological response and reproductive potential in gestating rabbit does.

Keywords: conception, haematology, moringa leaf extract, rabbit does

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223 The Effects of Maternal Exposure Riboflavin to Prevent Uterus Arsenic Damage in Offspring Rats

Authors: Ali Olfati, Parichehr Nouri


Objective: In this study, we have investigated for the first time in the literature the efficacy of riboflavin [VB2] in preventing uterus As₂O₃ damage. Methods: Rats received 40 μg LHRHa for estrus synchronization. 48 pregnant Wistar rats were included. Four groups were formed with 7 rats in each group: Sham, 1.5 mg arsenic trioxide (As₂O₃/L) alone or in combination with VB2 [20 and 40 mg/L] in drinking water [for 21 days continuously]. Similar to maternal generation treatment, the F1-female generation was also arranged [for 35 days continuously until puberty]. Results: Data indicated that As₂O₃ reduced body weight and feed intake (p<0.05). Furthermore, the serum malondialdehyde levels in the As₂O₃ group were significantly higher than that of the control group (p<0.05). At the same time, total antioxidative status and the activities of glutathione peroxidase, superoxide dismutase, and catalase were reduced (p<0.05). Meanwhile, As₂O₃ remarkably increased the production of inflammatory markers [interleukin 6 and C-reactive protein](p<0.05). As₂O₃ administration induced uterus apoptosis-related genes by upregulating caspase-3, iNOS, and Bax genes and downregulating Bcl-2 gene of pubertal F1-female rats (p<0.05). Conclusion: Our observation indicated that VB2 therapy is potentially an effective strategy to modifying the detrimental effects of As₂O₃ in pubertal F1-female rats via suppresses oxidative damages.

Keywords: As₂O₃, inflammation, puberty, vitamin B2

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222 Validity of a Timing System in the Alpine Ski Field: A Magnet-Based Timing System Using the Magnetometer Built into an IMU

Authors: Carla Pérez-Chirinos Buxadé, Bruno Fernández-Valdés, Mónica Morral-Yepes, Sílvia Tuyà Viñas, Josep Maria Padullés Riu, Gerard Moras Feliu


There is a long way to explore all the possible applications inertial measurement units (IMUs) have in the sport field. The aim of this study was to evaluate the validity of a new application on the use of these wearable sensors. Specifically, it was to evaluate a magnet-based timing system (M-BTS) for timing gate-to-gate in an alpine ski slalom using the magnetometer embedded in an IMU. This was a validation study. The criterion validity of time measured by the M-BTS was assessed using the 95% error-range against actual time obtained from photocells. The experiment was carried out with first-and second-year junior skiers performing a ski slalom on a ski training slope. Eight alpine skiers (17.4 ± 0.8 years, 176.4 ± 4.9 cm, 67.7 ± 2.0 kg, 128.8 ± 26.6 slalom FIS-Points) participated in the study. An IMU device was attached to the skier’s lower back. Skiers performed a 40-gate slalom from which four gates were assessed. The M-BTS consisted of placing four bar magnets buried into the snow surface, on the inner side of each gate’s turning pole; the magnetometer built into the IMU detected the peak-shaped magnetic field when passing near the magnets at a certain speed. Four magnetic peaks were detected. The time compressed between peaks was calculated. Three inter-gate times were obtained for each system: photocells and M-BTS. The total time was defined as the time sum of the inter-gate times. The 95% error intervals for the total time was 0.050 s for the ski slalom. The M-BTS is valid for timing gate-to-gate in an alpine ski slalom. Inter-gate times can provide additional data for analyzing skier’s performance, such as asymmetries between left and right foot.

Keywords: gate crossing time, inertial measurement unit, timing system, wearable sensor

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221 Improving Count Rate Capability of Timing RPCs by Increasing the Detector Working Temperature

Authors: A. Blanco, L. Lopes, J. Saraiva


Timing Resistive Plate Chambers (tRPC) is a mature and widely used gaseous detector (ALICEA at sign CERN, START at sign RHIC, or HADES at sign GSI) for the precise timing tag of charged particles exhibiting an excellent timing precision, down to 50 ps, together with high efficiency, larger than 98%, for minimum ionizing particles. Characteristics that can be implemented in large areas. tRPC has traditionally been used with relatively low particle loads (a few kHz/cm2) due to the inherent limitation to the counting rate imposed by the resistive electrodes. Since tRPCs are one of the main large-area timing detectors, the extension of its counting rate capability is of great interest for future HEP experiments, where the luminosity is expected to increase considerably. Attempts have already been made to increase the count rate capability by using materials with lower electrical resistivity compared to the commonly used float glass, such as ceramics, special glasses, or some technical plastics have already been done. As a result, the operation of small area detectors was successfully achieved, but the implementation of the medium/large area detectors failed due to the lack of homogeneity of the materials, which present low electrical resistivity paths, resulting in an unstable behavior of the detector. Another possibility, still very little explored, is to decrease the resistivity of standard float glass by increasing the operating temperature of the detectors, providing a ten-fold decrease in resistivity every 25ºC. In this communication, test beam results of common float glass RPCs operated up to 40 ºC are presented. The results suggest an improvement of the count rate capability by a factor of four compared with room temperature while keeping the timing precision and efficiency unchanged.

Keywords: gas detectors, RPCs, high counting rate, working temperature

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220 Buy-and-Hold versus Alternative Strategies: A Comparison of Market-Timing Techniques

Authors: Jonathan J. Burson


With the rise of virtually costless, mobile-based trading platforms, stock market trading activity has increased significantly over the past decade, particularly for the millennial generation. This increased stock market attention, combined with the recent market turmoil due to the economic upset caused by COVID-19, make the topics of market-timing and forecasting particularly relevant. While the overall stock market saw an unprecedented, historically-long bull market from March 2009 to February 2020, the end of that bull market reignited a search by investors for a way to reduce risk and increase return. Similar searches for outperformance occurred in the early, and late 2000’s as the Dotcom bubble burst and the Great Recession led to years of negative returns for mean-variance, index investors. Extensive research has been conducted on fundamental analysis, technical analysis, macroeconomic indicators, microeconomic indicators, and other techniques—all using different methodologies and investment periods—in pursuit of higher returns with lower risk. The enormous variety of timeframes, data, and methodologies used by the diverse forecasting methods makes it difficult to compare the outcome of each method directly to other methods. This paper establishes a process to evaluate the market-timing methods in an apples-to-apples manner based on simplicity, performance, and feasibility. Preliminary findings show that certain technical analysis models provide a higher return with lower risk when compared to the buy-and-hold method and to other market-timing strategies. Furthermore, technical analysis models tend to be easier for individual investors both in terms of acquiring the data and in analyzing it, making technical analysis-based market-timing methods the preferred choice for retail investors.

Keywords: buy-and-hold, forecast, market-timing, probit, technical analysis

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219 A Dual Spark Ignition Timing Influence for the High Power Aircraft Radial Engine Using a CFD Transient Modeling

Authors: Tytus Tulwin, Ksenia Siadkowska, Rafał Sochaczewski


A high power radial reciprocating engine is characterized by a large displacement volume of a combustion chamber. Choosing the right moment for ignition is important for a high performance or high reliability and ignition certainty. This work shows methods of simulating ignition process and its impact on engine parameters. For given conditions a flame speed is limited when a deflagration combustion takes place. Therefore, a larger length scale of the combustion chamber compared to a standard size automotive engine makes combustion take longer time to propagate. In order to speed up the mixture burn-up time the second spark is introduced. The transient Computational Fluid Dynamics model capable of simulating multicycle engine processes was developed. The CFD model consists of ECFM-3Z combustion and species transport models. A relative ignition timing difference for the both spark sources is constant. The temperature distribution on engine walls was calculated in the separate conjugate heat transfer simulation. The in-cylinder pressure validation was performed for take-off power flight conditions. The influence of ignition timing on parameters like in-cylinder temperature or rate of heat release was analyzed. The most advantageous spark timing for the highest power output was chosen. The conditions around the spark plug locations for the pre-ignition period were analyzed. This work has been financed by the Polish National Centre for Research and Development, INNOLOT, under Grant Agreement No. INNOLOT/I/1/NCBR/2013.

Keywords: CFD, combustion, ignition, simulation, timing

Procedia PDF Downloads 208
218 Timing and Impacts of Megafloods in the North Pacific as Recorded by Freshwater Diatoms

Authors: Cristina Lopes, Alan C. Mix


The timing and extension of large discharges from glacial lakes, known as megafloods, into the oceans have been of key importance. This type of events can influence the oceanic/land interactions and even be related with climate changes. While the impact of such floods has been fairly studied in the North Atlantic, the impact of analog floods in the North Pacific remains debatable and relatively unknown. Here we will show records of the Missoula floods that have carved the Northwest landscape and have entered the North Pacific through the Columbia River. These records are given by the presence of high (more than 40%) percentages of freshwater diatoms in marine sediments. A regression equation using these percentages allows to estimate by how much the salinities decreased. The timing and impact of North Pacific megafloods recorded in three marine cores of Oregon and California for the past 25000 years (B.P.) will be presented. These records show that the volume of freshwater that entered the North Pacific reached as far as 600 Km south of the Columbia River Mouth, decreasing the salinities by as much as 4 units.

Keywords: diatoms, megafloods, Missoula, North Pacific

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217 Estimating the Timing Interval for Malarial Indoor Residual Spraying: A Modelling Approach

Authors: Levicatus Mugenyi, Joaniter Nankabirwa, Emmanuel Arinaitwe, John Rek, Niel Hens, Moses Kamya, Grant Dorsey


Background: Indoor residual spraying (IRS) reduces vector densities and malaria transmission, however, the most effective spraying intervals for IRS have not been well established. We aim to estimate the optimal timing interval for IRS using a modeling approach. Methods: We use a generalized additive model to estimate the optimal timing interval for IRS using the predicted malaria incidence. The model is applied to post IRS cohort clinical data from children aged 0.5–10 years in selected households in Tororo, historically a high malaria transmission setting in Uganda. Six rounds of IRS were implemented in Tororo during the study period (3 rounds with bendiocarb: December 2014 to December 2015, and 3 rounds with actellic: June 2016 to July 2018). Results: Monthly incidence of malaria from October 2014 to February 2019 decreased from 3.25 to 0.0 per person-years in the children under 5 years, and 1.57 to 0.0 for 5-10 year-olds. The optimal time interval for IRS differed between bendiocarb and actellic and by IRS round. It was estimated to be 17 and 40 weeks after the first round of bendiocarb and actellic, respectively. After the third round of actellic, 36 weeks was estimated to be optimal. However, we could not estimate from the data the optimal time after the second and third rounds of bendiocarb and after the second round of actellic. Conclusion: We conclude that to sustain the effect of IRS in a high-medium transmission setting, the second rounds of bendiocarb need to be applied roughly 17 weeks and actellic 40 weeks after the first round, and the timing differs for subsequent rounds. The amount of rainfall did not influence the trend in malaria incidence after IRS, as well as the IRS timing intervals. Our results suggest that shorter intervals for the IRS application can be more effective compared to the current practice, which is about 24 weeks for bendiocarb and 48 weeks for actellic. However, when considering our findings, one should account for the cost and drug resistance associated with IRS. We also recommend that the timing and incidence should be monitored in the future to improve these estimates.

Keywords: incidence, indoor residual spraying, generalized additive model, malaria

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216 Removing Maturational Influences from Female Youth Swimming: The Application of Corrective Adjustment Procedures

Authors: Clorinda Hogan, Shaun Abbott, Mark Halaki, Marcela Torres Catiglioni, Goshi Yamauchi, Lachlan Mitchell, James Salter, Michael Romann, Stephen Cobley


Introduction: Common annual age-group competition structures unintentionally introduce participation inequalities, performance (dis)advantages and selection biases due to the effect of maturational variation between youth swimmers. On this basis, there are implications for improving performance evaluation strategies. Therefore the aim was to: (1) To determine maturity timing distributions in female youth swimming; (2) quantify the relationship between maturation status and 100-m FC performance; (3) apply Maturational-based Corrective Adjustment Procedures (Mat-CAPs) for removal of maturational status performance influences. Methods: (1) Cross-sectional analysis of 663 female (10-15 years) swimmers who underwent assessment of anthropometrics (mass, height and sitting height) and estimations of maturity timing and offset. (2) 100-m front-crawl performance (seconds) was assessed at Australian regional, state, and national-level competitions between 2016-2020. To determine the relationship between maturation status and 100-m front-crawl performance, MO was plotted against 100-m FC performance time. The expected maturity status - performance relationship for females aged 10-15 years of age was obtained through a quadratic function (y = ax2 + bx + c) from unstandardized coefficients. The regression equation was subsequently used for Mat-CAPs. (3) Participants aged 10-13 years were categorised into maturity-offset categories. Maturity offset distributions for Raw (‘All’, ‘Top 50%’ & ‘Top 25%’) and Correctively Adjusted swim times were examined. Chi-square, Cramer’s V and ORs determined the occurrence of maturation biases for each age group and selection level. Results—: (1) Maturity timing distributions illustrated overrepresentation of ‘normative’ maturing swimmers (11.82 ± 0.40 years), with a descriptive shift toward the early maturing relative to the normative population. (2) A curvilinear relationship between maturity-offset and swim performance was identified (R2 = 0.53, P < 0.001) and subsequently utilised for Mat-CAPs. (3) Raw maturity offset categories identified partial maturation status skewing towards biologically older swimmers at 10/11 and 12 years, with effect magnitudes increasing in the ‘Top 50%’ and ‘25%’ of performance times. Following Mat-CAPs application, maturity offset biases were removed in similar age groups and selection levels. When adjusting performance times for maturity offset, Mat-CAPs was successful in mitigating against maturational biases until approximately 1-year post Peak Height Velocity. The overrepresentation of ‘normative’ maturing female swimmers contrasted with the substantial overrepresentation of ‘early’ maturing male swimmers found previously in 100-m front-crawl. These findings suggest early maturational timing is not advantageous in females, but findings associated with Aim 2, highlight how advanced maturational status remained beneficial to performance. Observed differences between female and male maturational biases may relate to the differential impact of physiological development during pubertal years. Females experience greater increases of fat mass and potentially differing changes in body shape which can negatively affect swim performance. Conclusions: Transient maturation status-based participation and performance advantages were apparent within a large sample of Australian female youth 100-m FC swimmers. By removing maturity status performance biases within female youth swimming, Mat-CAPs could help improve participation experiences and the accuracy of identifying genuinely skilled female youth swimmers.

Keywords: athlete development, long-term sport participation, performance evaluation, talent identification, youth competition

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215 The Study of Tire Pyrolysis Fuel in CI Diesel Engine for Spray Combustion Character and Performance

Authors: Chun Pao Kuo, Chi Tong Lin


The study explored atomization characteristics of tire pyrolysis fuel and its impacts on using three types of fuel: diesel oil mixed with 10% of tire pyrolysis fuel (called T10), diesel oil mixed with 20% tire pyrolysis (called T20), and consumer-grade diesel oil (D100). The investigators used the fuel for simulation and tests at various fuel injection timing, engine speed, and fuel injection speed to inspect impacts from fuel type on oil droplet atomization speed and output power. Actual vehicle tests were conducted using a 5-ton sedan (Hino) with 3660 cc displacement and a front-end inline four-cylinder diesel engine, and this type of vehicle is easily available from the market. A dynamometer was used to set up three engine speeds for the dynamometer testing at different injection timing and pressure. Next, an exhaust analyzer was used to measure exhaust pollution at different conditions to explore the effect of fuel types and injection speeds on output power in order to establish the best operation conditions for tire pyrolysis fuel.

Keywords: diesel engine, exhaust pollution, fuel injection timing, tire pyrolysis oil

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214 Speech Rhythm Variation in Languages and Dialects: F0, Natural and Inverted Speech

Authors: Imen Ben Abda


Languages have been classified into different rhythm classes. 'Stress-timed' languages are exemplified by English, 'syllable-timed' languages by French and 'mora-timed' languages by Japanese. However, to our best knowledge, acoustic studies have not been unanimous in strictly establishing which rhythm category a given language belongs to and failed to show empirical evidence for isochrony. Perception seems to be a good approach to categorize languages into different rhythm classes. This study, within the scope of experimental phonetics, includes an account of different perceptual experiments using cues from natural and inverted speech, as well as pitch extracted from speech data. It is an attempt to categorize speech rhythm over a large set of Arabic (Tunisian, Algerian, Lebanese and Moroccan) and English dialects (Welsh, Irish, Scottish and Texan) as well as other languages such as Chinese, Japanese, French, and German. Listeners managed to classify the different languages and dialects into different rhythm classes using suprasegmental cues mainly rhythm and pitch (F0). They also perceived rhythmic differences even among languages and dialects belonging to the same rhythm class. This may show that there are different subclasses within very broad rhythmic typologies.

Keywords: F0, inverted speech, mora-timing, rhythm variation, stress-timing, syllable-timing

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213 The Effects of Source and Timing on the Acceptance of New Product Recommendation: A Lab Experiment

Authors: Yani Shi, Jiaqi Yan


A new product is important for companies to extend consumers and manifest competitiveness. New product often involves new features that consumers might not be familiar with while it may also have a competitive advantage to attract consumers compared to established products. However, although most online retailers employ recommendation agents (RA) to influence consumers’ product choice decision, recommended new products are not accepted and chosen as expected. We argue that it might also be caused by providing a new product recommendation in the wrong way at the wrong time. This study seeks to discuss how new product evaluations sourced from third parties could be employed in RAs as evidence of the superiority for the new product and how the new product recommendation could be provided to a consumer at the right time so that it can be accepted and finally chosen during the consumer’s decision-making process. A 2*2 controlled laboratory experiment was conducted to understand the selection of new product recommendation sources and recommendation timing. Human subjects were randomly assigned to one of the four treatments to minimize the effects of individual differences on the results. Participants were told to make purchase choices from our product categories. We find that a new product recommended right after a similar existing product and with the source of the expert review will be more likely to be accepted. Based on this study, both theoretical and practical contributions are provided regarding new product recommendation.

Keywords: new product recommendation, recommendation timing, recommendation source, recommendation agents

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212 Drip Irrigation Timing and Its Effect on Tomato Yield for a Two-Day Schedule

Authors: T. Kizza, M. Muyinda


Irrigation schedules are normally given in terms of frequency (irrigation days). Specific timings within a given day are not usually included. This study examined the effect of irrigation timing for a two-day irrigation schedule of a surface drip-irrigated tomato field on yield. It was carried out for three dry seasons; July-Sept 2016, Jan-April 2017 and Jan-March 2018, at MuZARDI research station. Four irrigation treatments; T1 morning (8.00hrs), T2 noon (12:00hrs), T3 evening (17:00hr) and T4, a combination of morning and evening, were evaluated. The irrigation duration was one hour for T1-T3 and split into 30 minutes for T4. First season results indicated noon watering as having the best yield over other treatments at 51.59t/ha followed closely by morning watering at 50.6t/ha. Plants watered at noon had the highest number of fruits at 19/plant with an average weight of 94g/fruit. Plants watered in the morning had fruits with the highest average weight at 111.2g/fruit but they were the lowest number at 16 fruits/plant. The three-season data indicated the highest yield at 45.9t/ha for morning watering, followed by noon watering at 44.3t/ha and the least yield was for evening watering at 40.9t/ha. Watering tomatoes in the morning will give optimum yields for a two-day irrigation schedule.

Keywords: drip irrigation, irrigation schedule, irrigation timing, tomato yield

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211 Efficient Control of Some Dynamic States of Wheeled Robots

Authors: Boguslaw Schreyer


In some types of wheeled robots it is important to secure starting acceleration and deceleration maxima while at the same time maintaining transversal stability. In this paper torque distribution between the front and rear wheels as well as the timing of torque application have been calculated. Both secure an optimum traction coefficient. This paper also identifies required input signals to a control unit, which controls the torque values and timing. Using a three dimensional, two mass model of a robot developed by the author a computer simulation was performed confirming the calculations presented in this paper. These calculations were also implemented and confirmed during military robot testing.

Keywords: robot dynamics, torque distribution, traction coefficient, wheeled robots

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210 The Possibility of Solving a 3x3 Rubik’s Cube under 3 Seconds

Authors: Chung To Kong, Siu Ming Yiu


Rubik's cube was invented in 1974. Since then, speedcubers all over the world try their best to break the world record again and again. The newest record is 3.47 seconds. There are many factors that affect the timing, including turns per second (tps), algorithm, finger trick, hardware of the cube. In this paper, the lower bound of the cube solving time will be discussed using convex optimization. Extended analysis of the world records will be used to understand how to improve the timing. With the understanding of each part of the solving step, the paper suggests a list of speed improvement techniques. Based on the analysis of the world record, there is a high possibility that the 3 seconds mark will be broken soon.

Keywords: Rubik's Cube, speed, finger trick, optimization

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209 Self Tuning Controller for Reducing Cycle to Cycle Variations in SI Engine

Authors: Alirıza Kaleli, M. Akif Ceviz, Erdoğan Güner, Köksal Erentürk


The cyclic variations in spark ignition engines occurring especially under specific engine operating conditions make the maximum pressure variable for successive in-cylinder pressure cycles. Minimization of cyclic variations has a great importance in effectively operating near to lean limit, or at low speed and load. The cyclic variations may reduce the power output of the engine, lead to operational instabilities, and result in undesirable engine vibrations and noise. In this study, spark timing is controlled in order to reduce the cyclic variations in spark ignition engines. Firstly, an ARMAX model has developed between spark timing and maximum pressure using system identification techniques. By using this model, the maximum pressure of the next cycle has been predicted. Then, self-tuning minimum variance controller has been designed to change the spark timing for consecutive cycles of the first cylinder of test engine to regulate the in-cylinder maximum pressure. The performance of the proposed controller is illustrated in real time and experimental results show that the controller has a reliable effect on cycle to cycle variations of maximum cylinder pressure when the engine works under low speed conditions.

Keywords: cyclic variations, cylinder pressure, SI engines, self tuning controller

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208 Effect of Low to Moderate Altitude on Football Performance: An Analysis of Thirteen Seasons in the South African Premier Soccer League

Authors: Khatija Bahdur, Duane Dell’Oca


There is limited information on how altitude impacts performance in a team sport. Most altitude research in football has been conducted at high elevation ( > 2500m), resulting in a chasm of understanding whether low to moderate altitude affects performance. The South African Premier Soccer League (PSL) fixtures entail matches played at altitudes from sea level to 1700m above mean sea level. Despite coaches highlighting the effect of altitude on performance outcomes in matches, further research is needed to establish whether altitude does impact match results. Greater insight into if and how altitude impacts performance in the PSL will assist coaches in deciding if and how to incorporate altitude in their planning. The purpose of this study is to fill in this gap through the use of a retrospective analysis of PSL matches. This quantitative study is based on a descriptive analysis of 181 PSL matches involving one team based at sea-level, taking place over a period of thirteen seasons. The following data were obtained: altitude at which the match was played, match result, the timing of goals, and timing of substitutions. The altitude was classified in 2 ways: inland ( > 500m) and coastal ( < 500m) and also further subdivided into narrower categories ( < 500m, 500-1000m, 1000-1300m; 1300-1500m, > 1500m). The analysis included a 2-sample t-test to determine differences in total goals scored and timing of goals for inland and coastal matches and the chi-square test to identify the significance of altitude on match results. The level of significance was set at the alpha level of 0.05. Match results are significantly affected by the altitude and level of altitude within inland teams most likely to win when playing at inland venues (p=0.000). The proportion of draws was slightly higher at the coast. At altitudes between 500-1000m, 1300-1500m, and 1500-1700m, a greater percentage of matches were won by coastal teams as opposed to draws. The timing of goals varied based on the team’s base altitude and the match elevation. The most significant differences were between 36-40 minutes (p=0.023), 41-45 minutes (p=0.000) and 50-65 minutes (p=0.000). When breaking down inland team’s matches to different altitude categories, greater differences were highlighted. Inland teams scored more goals per minute between 10-20 minute (p=0.009), 41-45 minutes (p=0.003) and 50-65 minutes (p=0.015). The total number of goals scored per match at different altitudes by a) inland teams (p=0.000), b) coastal teams (p=0.006). Coastal teams made significantly more substitutions when playing at altitude (p=0.034), although there were no significant differences when comparing the different altitude categories. The timing of all three changes, however, did vary significantly at the different altitudes. There were no significant differences in timing or number of substitutions for inland teams. Match results and timing of goals are influenced by altitude, with differences between the level of altitude also playing a role. The trends indicate that inland teams win more matches when playing at altitude against coastal teams, and they score more goals just prior to half-time and in the first quarter of the second half.

Keywords: coastal teams, inland teams, timing of goals, results, substitutions

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