scholarly journals Влияние широкополосной частотной модуляции на конкуренцию ортогонально поляризованных мод двухмодового лазера

2019 ◽  
Vol 45 (10) ◽  
pp. 52
Author(s):  
В.И. Воронов
Keyword(s):  
Numerical Model ◽  
Active Medium ◽  
Modulation Frequency ◽  
Frequency Deviation ◽  
Negative Effects ◽  
Mode Laser ◽  
Gain Line ◽  
Broadband Frequency

The intermode competition of orthogonally polarized modes in a broadband frequency modulated double-mode laser within a numerical model was investigated. The modulation is implemented by a corresponding change in the length of the resonator. Parameters of the active medium correspond to He-Ne lasers with an inhomogeneous broadened gain line. It is shown that negative effects of the competition can be significantly reduced at certain values of the modulation frequency and the frequency deviation.

Local Scouring Characteristics Downstream of Arched Cross-Vane Structures

2020 ◽  
Author(s):  
You-Wei Lai ◽  
Po-An Chen ◽  
Hsun-Chuan Chan
Keyword(s):  
Numerical Model ◽  
Flow Rate ◽  
Scour Depth ◽  
Negative Effects ◽  
Scour Holes ◽  
The Cross ◽  
Type 3 ◽  
Geometrical Dimensions

<p>Groundsill is one of the hydraulic structures used to stabilize the riverbed and prevent the erosion of riverbank. Therefore, groundsill may have the negative effects on the ecological environment. Comparing with a traditional groundsill, a Cross-Vane concentrates the water flow and create a downstream pool. This may improve the diversity of the aquatic habitats. The aim of this research is to analyze the scour phenomena and morphologies downstream of an arched Cross-Vane with different geometrical dimensions in a straight channel by using the numerical model. The riverbed slopes of 0%, 2%, 4% and 6% were tested. Among them, the ratio (<em>L/B</em>) between the arc length of the structure (<em>L</em>) and the channel width (<em>B</em>) represents the camber of structures, including 13 kinds of arches. For each arch structure, Densimetric Froude numbers (<em>F<sub>d</sub></em>) , approach flow depths (<em>h<sub>0</sub></em>) and drop heights (<em>Δy</em>) were tested in different flow rate, and the flow rate was between 0.01cms and 0.04cms.The results showed the downstream scour pattern of the arched Cross-Vane had a significant correlation with <em>F<sub>d</sub></em> and <em>Δy</em>, and could be classified according to the scour length (<em>l<sub>m</sub></em>) and the ridge length (<em>l<sub>n</sub></em>). Scour typology included five types of scour. Type 1 : <em>l<sub>m</sub>/B</em> > 2.5 and <em>l<sub>n</sub> /B</em> < 1. Type 2: <em>l<sub>m</sub>/B</em> was located about 2.0 to 2.5 and l<em><sub>n</sub>/B > 1. </em>Type 3: <em>l<sub>m</sub>/B=</em>2.0 and<em> l<sub>n</sub>/B</em> < 1. Type 4: <em>l<sub>m</sub>/B</em> was located about 1.5 to 2.0 and <em>l<sub>n</sub>/B</em> > 1. Type 5 : <em>l<sub>m</sub>/B</em> < 1.5 and<em> l<sub>n</sub> /B</em> > 1. <em>L/B</em> was one of the most important parameters affecting the maximum scour depth and its position. When <em>L/B</em> was less than 1.4, the scour holes were similar to the traditional groundsill. When the<em> L/B</em> ranged between 1.4 and 2.3, the maximum scour depth was located at about 0.5 to 0.65 times of scour length downstream the Cross-Vane. When<em> L/B</em> was greater than 2.3, the maximum scour depth was located adjacent to the Cross-Vane.</p><p><strong>Keyword : </strong>Cross-vane, Scour morphology, Numerical model</p>

Flow structure in the frequency-modulated wake of a cylinder

1994 ◽  
Vol 266 ◽  
pp. 93-119 ◽  
Author(s):  
M. Nakano ◽  
D. Rockwell
Keyword(s):  
Flow Structure ◽  
Modulation Frequency ◽  
Excitation Frequency ◽  
Frequency Deviation ◽  
Near Wake ◽  
Spectral Content ◽  
Wake Structure ◽  
Vortical Structures ◽  
Far Wake ◽  
Sinusoidal Excitation

A cylinder is subjected to frequency-modulated (FM) excitation and the structure of its wake is characterized in terms of the modulation frequency and the frequency deviation. It is possible to destabilize or restabilize the degree of organization of the vortical structures in the near wake and thereby substantially manipulate the spectral content, relative to the case of purely sinusoidal excitation. These processes of destabilization and restabilization are attainable by varying the frequency deviation while holding the modulation frequency constant or vice versa. A phase-locked periodicity of the nearwake response is attainable at the period of the modulation frequency, as well as at double its period. This phase-locked periodicity, or lack of it, is related to the degree of organization of the wake. The structure of the far wake is strongly dependent upon the nature of the near wake modification. Either coherent or destabilized wake structure can be induced in the far wake, at a given value of nominal excitation frequency, by employing appropriate FM excitation.

scholarly journals Research of metrological capabilities of digital (DDS- and Trueform-) generators

2021 ◽  
pp. 3-9
Author(s):  
Yurii Pavlenko ◽  
Sergii Kirienko ◽  
Valeriy Ogar ◽  
Olena Vаsileva
Keyword(s):  
Amplitude Modulation ◽  
Frequency Modulation ◽  
Nonlinear Distortion ◽  
Modulation Frequency ◽  
Frequency Deviation ◽  
Frequency Noise ◽  
Direct Digital Synthesis ◽  
Modulation Mode ◽  
Nonlinear Distortions ◽  
Digital Synthesis

Abstract One of the fundamental improvements of the measurement standard of frequency deviation of frequency-modulated oscillations was the replacement of analog frequency-modulated generators used in DETU 09-03-95 with digital ones based on the principle of direct digital synthesis (DDS) and its next version of Trueform technology. These generators have wider ranges of frequency deviation and modulation frequencies than analog ones, but nonlinear distortion laws of the frequency modulation are not standardized. The subject of the article is the development of methods and research of these generators and frequency-modulated signals generated by them for nonlinear distortions, accompanying amplitude modulation, frequency noise. Three methods were used in the study: direct measurement; “combination frequencies” and “frequency shift”. The experiment was performed using several measurement methods, which allowed to estimate very small values of nonlinear distortion. Methods were developed and experimental estimations of concomitant amplitude modulation of DDS-generators (in frequency modulation mode), as well as their frequency noise level, were performed. An experimental evaluation of the capabilities of the analog-digital demodulator of the R&S FSL6 spectrum analyzer with the K7 option was performed, its high linearity was shown, its capabilities with respect to the frequency ranges of carrier oscillations and frequency deviation were evaluated. The research results provide a basis for the method of calibration of DDS-generators and demodulator of spectrum analyzers with the K7 option in those ranges where their parameters are not normalized (at direct current up to 8 MHz and F up to 500 kHz).

scholarly journals Potential effects of climate change on northwest Portuguese coastal zones

2009 ◽  
Vol 66 (7) ◽  
pp. 1497-1507 ◽  
Author(s):  
Carlos Coelho ◽  
Raquel Silva ◽  
Fernando Veloso-Gomes ◽  
Francisco Taveira-Pinto
Keyword(s):  
Climate Change ◽  
Numerical Model ◽  
Coastal Erosion ◽  
Wave Action ◽  
Coastal Zones ◽  
Negative Effects ◽  
Coastal Evolution ◽  
Shoreline Evolution ◽  
Environmental Actions ◽  
Anthropogenic Intervention

Abstract Coelho, C., Silva, R., Veloso-Gomes, F., and Taveira-Pinto, F. 2009. Potential effects of climate change on northwest Portuguese coastal zones. – ICES Journal of Marine Science, 66: 1497–1507. Coastal erosion is a common problem in Europe; a result of the dynamic nature of its coastal zones, of anthropogenic influences, such as coastal interventions and littoral occupation, and of the effects of climate change. The increase in the occurrence of extreme events, the weakening of river-sediment supplies, and the general acceleration of sea level rise (SLR) probably tends to aggravate coastal erosion on decadal time-scales. Describing vulnerability and risk patterns for energetic environmental actions is important for coastal planning and management to rationalize the decision-making process. To minimize negative effects, the various processes causing erosion must be understood to assess the possible prediction scenarios for coastal evolution in the medium to long term. This paper describes the application of a coastal (shoreline evolution) numerical model to a stretch of the Portuguese coast to determine the effects of various scenarios of wave action and SLR that might result from climate change over the next 25 years. We conclude that the effects of SLR are less important than changes in wave action. The numerical model was also applied in a generic situation to compare shoreline evolution with and without anthropogenic intervention.

Model Tests to Assess Wave and Current Loads on Ocean Cleanup’s Conceptual Plastic Capturing Barrier

2017 ◽  
Author(s):  
Joost Sterenborg ◽  
Mark Paalvast ◽  
Willem van Schoten ◽  
Lourens Boot ◽  
Arjen Tjallema
Keyword(s):  
Numerical Model ◽  
Flow Direction ◽  
Model Tests ◽  
Fluid Structure Interactions ◽  
Plastic Pollution ◽  
Negative Effects ◽  
Vertical Orientation ◽  
Design Concepts ◽  
Flexible Barrier ◽  
Barrier Performance

Lot of plastics enters the ocean every day with negative effects on the environment, economy and health. A large portion of the floating plastics accumulate in so-called gyres, where currents converge. One of the aims of the Ocean Cleanup is to develop technologies to extract plastic pollution from the oceans. The idea is to install a flexible barrier in the ocean that is supposed to concentrate the plastic at the Great Pacific Garbage Patch. The design of the barrier is still in the conceptual phase and the model tests described in this report are conducted to assist in the development of the barrier. The model tests were carried out in MARIN’s Offshore Basin and served two main goals: 1) provide loads and displacements for numerical model calibrations and 2) examine the 3D fluid-structure interactions and the barrier performance for three different design concepts. A 360m prototype length barrier was considered that consists of a floater with a diameter of 1.5m and a screen with a height of 2m. To model larger lengths of the barrier, various pretensions were applied at the ends of the barrier. For the secondary mooring concept the barrier was moored each 60m via the bottom of the screen to a submerged tension line. For the low mooring and high mooring concepts, the model was only moored at both ends of the bottom of the screen or bottom of the floater. In general mooring loads were found to be the largest for the low mooring configuration. For this same configuration the mooring loads increment with increasing current velocity was the largest. Mooring load fluctuations seemed to be not strongly influenced by the amount of applied pretension. Vertical screen orientations, which are expected to be beneficial for the plastic capturing efficiency, were mostly observed for the secondary mooring and high mooring configurations. For the low mooring concept the offsets along the flow direction were the largest and the screen was more tilted. Additional ballast for the high mooring concept promoted a more vertical orientation of the screen with as downside increasing mooring loads. Overtopping or bridging (air gap exists below the barrier) negatively impact the plastic capturing efficiency and are important to consider. Both events are most likely to happen for shorter wave conditions and higher current velocities. The number of occurrences of overtopping and bridging was the lowest for the secondary mooring and the high mooring setup with a low pretension. For increasing pretension the number of overtopping and bridging events increased.

Undesirable Effects of Goal Setting on Perceived Fairness, Commitment, and Unethical Behavior

2018 ◽  
Vol 62 (2) ◽  
pp. 97-107 ◽  
Author(s):  
Nina Keith
Keyword(s):  
Goal Setting ◽  
Unethical Behavior ◽  
The United States ◽  
Goal Commitment ◽  
Management Technique ◽  
Long Term Effects ◽  
Perceived Fairness ◽  
Negative Effects ◽  
Positive Effects ◽  
And Performance

Abstract. The positive effects of goal setting on motivation and performance are among the most established findings of industrial–organizational psychology. Accordingly, goal setting is a common management technique. Lately, however, potential negative effects of goal-setting, for example, on unethical behavior, are increasingly being discussed. This research replicates and extends a laboratory experiment conducted in the United States. In one of three goal conditions (do-your-best goals, consistently high goals, increasingly high goals), 101 participants worked on a search task in five rounds. Half of them (transparency yes/no) were informed at the outset about goal development. We did not find the expected effects on unethical behavior but medium-to-large effects on subjective variables: Perceived fairness of goals and goal commitment were least favorable in the increasing-goal condition, particularly in later goal rounds. Results indicate that when designing goal-setting interventions, organizations may consider potential undesirable long-term effects.

The Effect of Suicide-Related Internet Use on Users’ Mental Health

Crisis ◽  
2013 ◽  
Vol 34 (5) ◽  
pp. 348-353 ◽  
Author(s):  
Hajime Sueki
Keyword(s):  
Mental Health ◽  
Young Adults ◽  
Suicidal Ideation ◽  
Internet Use ◽  
Panel Study ◽  
Psychological Effects ◽  
The Internet ◽  
Negative Effects ◽  
Suicide Methods ◽  
Internet Users

Background: Previous studies have shown that suicide-related Internet use can have both negative and positive psychological effects. Aims: This study examined the effect of suicide-related Internet use on users’ suicidal ideation, depression/anxiety tendency, and loneliness. Method: A two-wave panel study of 850 Internet users was conducted via the Internet. Results: Suicide-related Internet use (e.g., browsing websites about suicide methods) had negative effects on suicidal ideation and depression/anxiety tendency. No forms of suicide-related Internet use, even those that would generally be considered positive, were found to decrease users’ suicidal ideation. In addition, our results suggest that the greater the suicidal ideation and feelings of depression and loneliness of Internet users, the more they used the Internet. Conclusion: Since suicide-related Internet use can adversely influence the mental health of young adults, it is necessary to take measures to reduce their exposure to such information.

Searching Online for Methods of Suicide

Crisis ◽  
2020 ◽  
pp. 1-8
Author(s):  
Christian Ulrich Eriksen ◽  
Flemming Konradsen ◽  
Thilde Vildekilde
Keyword(s):  
Content Analysis ◽  
English Language ◽  
Significant Proportion ◽  
Background Information ◽  
Access To Information ◽  
Online Content ◽  
Negative Effects ◽  
Search Terms ◽  
Methods Of Suicide

Abstract. Background: Information on methods of suicide is available online, and access to information on methods of suicide appears to contribute to a small but significant proportion of suicides. There is limited documentation of how methods of suicide are being profiled, as well as what content exists in other languages than English. Aim: We aimed to analyze and compare how methods of suicide are profiled on Danish and English-language websites. Method: We applied a categorization and content analysis of websites describing methods of suicide. Sites were retrieved by applying widely used Danish and English-language search terms. Results: A total of 136 English-language websites and 106 Danish-language websites were included for analysis. Websites were more often categorized as prevention or support sites, academic or policy sites, and against suicide sites than dedicated suicide sites (i.e., pro-suicide sites), or information sites. However, information on methods of suicide was available, and 20.1% and 8.9% of the English and Danish-language sites, respectively, suggested that a particular method of suicide was quick, easy, painless, or certain to result in death. Limitations: Only one author coded and analyzed all websites. A further operationalization of the content analysis checklist is warranted to increase reliability. Conclusion: The websites primarily had a prevention or anti-suicide focus, but information on methods of suicide was available, requiring an increased focus on how to diminish the negative effects of harmful online content.

Effectiveness of Programs for the Prevention of Child Sexual Abuse

2020 ◽  
Vol 25 (1) ◽  
pp. 1-15 ◽  
Author(s):  
Amaia Del Campo ◽  
Marisalva Fávero
Keyword(s):  
United States ◽  
Sexual Abuse ◽  
New Zealand ◽  
Critical Analysis ◽  
Prevention Programs ◽  
The United States ◽  
Sexual Abuse Prevention ◽  
Negative Effects ◽  
The United Kingdom ◽  
Methodological Considerations

Abstract. During the last decades, several studies have been conducted on the effectiveness of sexual abuse prevention programs implemented in different countries. In this article, we present a review of 70 studies (1981–2017) evaluating prevention programs, conducted mostly in the United States and Canada, although with a considerable presence also in other countries, such as New Zealand and the United Kingdom. The results of these studies, in general, are very promising and encourage us to continue this type of intervention, almost unanimously confirming its effectiveness. Prevention programs encourage children and adolescents to report the abuse experienced and they may help to reduce the trauma of sexual abuse if there are victims among the participants. We also found that some evaluations have not considered the possible negative effects of this type of programs in the event that they are applied inappropriately. Finally, we present some methodological considerations as critical analysis to this type of evaluations.

If I Had Something to Add, I Would

2020 ◽  
Vol 19 (2) ◽  
pp. 86-96
Author(s):  
Isaac A. Lindquist ◽  
Emily E. Adams ◽  
Joseph A. Allen
Keyword(s):  
Job Attitudes ◽  
Negative Effects ◽  
Meeting Effectiveness ◽  
And Behavior ◽  
Attitudes And Behavior

Abstract. Most employees participate in workplace meetings, and their experiences in meetings can vary greatly, which can lead to positive or negative effects on both job attitudes and behavior. In this study, we examined the effect that a meeting attendee’s competence in the meeting topic had on their participation in the meeting and their perception of meeting effectiveness. Results indicated those with higher levels of competence in the meeting topic were more likely to participate and through participation found their meeting more effective; this relationship was stronger when employee dissent in the meetings was high. Leaders should ensure that those who are present in a meeting are competent in the topic of the meeting and encourage them to participate.

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