Resonances and Synchronization in Two Coupled Oscillators with Stick-Slip Vibrations and Spring Pendulums

We study the dynamical behavior of a system of two coupled mechanical oscillators with spring pendulums and driven by a stick-slip induced vibrations. Each of the oscillator consists of the body placed onto a moving belt/foundation, mechanical coupling associated with the body load pressed the belt depending on the body movement as well as suspended spring pendulum. In addition, the influence of the presence of additional electric/electromagnetic forces acting on the pendulums are analyzed. Different kinds of resonance behavior can be found in the studied system, even if it is simplified to a single degree-of-freedom system. As a result, due to many degrees-of-freedom and strong nonlinearity and discontinuity of the considered system, novel nonlinear dynamical phenomena occur, both near and beyond to the resonance. The motion analysis for different cases is carried out by employing standard numerical methods dedicated for nonlinear systems, including both qualitative and quantitative methods, as well as original animations of the system dynamics created in Mathematica. Understanding the role of coupling, transition between fixed points and energy transition in the considered system can be potentially applied in other similar systems, especially in real electro-mechanical systems, power system or in structural engineering

Power consumption analysis of different hexapod robot gaits.

The paper is focused on the power consumption analysis of different gaits of our constructed hexapod robot controlled by different Central Pattern Generator (CPG) models. There are a lot of gait patterns in the literature constructed either by different CPG models or using a series of oscillations with adjustable phase lag. The mentioned models, as well as those proposed in our previous paper are used and compared from the viewpoint of energy demand. In general, power consumption of the constructed hexapod robot is experimentally analyzed based on the current consumption in the applied servo motors, which drive the robot limbs. For this purpose the suitable drivers allowing a simple measurement of electric energy consumption of servo motors are used. The obtained experimental results show different energy demand for different robot gaits. Because power consumption is one of the main operational restrictions imposed on autonomous walking robots, we show that the performed energy efficiency analysis and the choice of the appropriate robot gaits depending on the actual situation can reduce the energy costs

Dynamics of two coupled 4-DOF mechanical linear sliding systems with dry friction.

The paper introduces a model of two identical coupled 4-DOF mechanical linear sliding systems with dry friction coupled with each other by a linear torsional spring. The appropriate components (bodies) of the coupled systems are riding on two separated driving belts, which are driven at constant velocities, and stick-slip vibrations can be observed. In this case the physical interpretation of the considered model could be two rows of carriages laying on the guideways and coupled by an elastic shaft, which are moving at constant velocity with respect to the guideways as a foundation. From a mathematical point of view the analyzed problem is governed by eight nonlinear ordinary second order differential equations of motion yielded by the second kind Lagrange equations. Numerical analysis is performed in Mathematica software using the qualitative and quantitative theories of differential equations. Some interesting non-linear system dynamics are detected and reported using the phase portraits and the Poincaré maps. Next, power spectra obtained by the FFT technique are reported. The presented results show periodic, quasi-periodic, chaotic and hyperchaotic orbits. Moreover, synchronization effects between the coupled systems are also detected and studied

Świeckość państwa zakwestionowana we Włoszech. Debata na temat krzyży w szkolnych klasach.

In November 2009 the European Court of Human Rights in Strasbourg ruled that crosses displayed in classrooms of public school are not in agreement with the freedom of religion guaranteed by the European Convention on Human Rights. This ruling was based on the claim that the presence of the Christian symbol limit parents’ right to educate their children in conformity with their own faith and the right of children to believe or not to believe. In Italy, from which the case originates, the Court’s sentence stirred up heated political debates and caused strong public opinion reactions. The verdict was interpreted as a threat to the Catholic-based cultural traditions of the country, despite the traditions not being continued in terms of religious devotion in Italy

Threading on thin ice? Conflict dynamics on the Korean Peninsula

In 2018, both the Republic of Korea (ROK) and the Democratic People’s Republic of Korea (DPRK) will mark the 70th anniversary of the establishment of their separate governments. This is a sad reminder that much remains frozen on the Korean Peninsula. For one, families have been separated and communication channels between the two Korean populations are almost non-existent. Yet, stability is precariously established by an Armistice that was signed in 1953 and that was never replaced by a permanent peace mechanism. Moreover, North Korea’s rapid nuclear development has contributed to tensions and uncertainties, and the Six-Party Talks, originally designed to ensure the denuclearisation of the peninsula, has been at a standstill for almost 10 years. The Korean story is thus a prime case to study the dynamics of a frozen conflict and this article contributes to the existing literature and analysis of frozen conflicts by suggesting looking at peaceful and violent thawing, as well as conflict withering. In order to so, the paper focuses on three crucial levels: (1) the micro level, the impact of the Armistice in light of today’s Koreas as opposed to their status and standing at the end of the Korean War in 1953, (2) the meso level with geostrategic concerns concentrated over sectorial policies surrounding the Korean Peninsula in a globalised world, and (3) the macro level with the changing nature of security governance. It is argued that in a catch-22 motion, the thread of violent thawing maintains the conflict in its frozen state

Carrots and sticks:The construction of an American foreign policy toward North Korea

The United States' involvement on the Korean peninsula has always oscillated between extremes, especially when dealing with the Democratic People's Republic of Korea and Washington has used a variety of policies ranging from engagement to threats in order to try to steer North Korea out of a seemingly roguish path. Some argue that American sanctions have been rather ineffective at pressuring Kim Jong-il's dictatorship since both China and South Korea have been helping North Korea financially, thus largely offsetting the sanctions' effects. However, others have stated that in order for an agreement to be reached, Pyongyang would have to receive assurance that its regime would not be toppled. Therefore, a review of American foreign policy actions toward North Korea will provide instruction on how to deal with a nuclear North Korea, especially in light of the 2008 American Presidential election

New approaches to North Korean politics after reunification:the search for a common Korean identity

Whilst most of the literature focusing on the Korean peninsula has concentrated on how to achieve unification through confidence-building measures, dialogues, negotiation and diplomacy, little attention has been paid to how a unified Korean identity, a core component of any potential reunification scheme could develop and be sustained. The paper addresses this gap by: (1) defining what national identity is, and how Korean identities have been formed, (2) outlining how both South and North Korea have understood and used the concept of national identity, (3) suggesting possible grounds on which the two Koreas could build a new, common national identity

From Balancing to Bandwagoning: Evaluating the Impact of the Sanction Regime on North Korea–Africa Relationships

Purpose—The DPRK has maintained an extensive array of foreign relationships over the past decades, both for political and economic gains. This article evaluates the impact of the current sanction regime on the DPRK’s activities with African countries. Design/Methodology/Approach—The analysis is conducted by using a bespoke behavior framework based on Stephen Walt’s “balance of threat” theory. This framework develops the concepts of balancing, defensive bandwagoning, and opportunistic bandwagoning as potential behaviors of African states following the imposition of United Nations Security Council Resolutions to sanction North Korea from 2006 until 2017. Findings—Evidence suggests that some long- standing relationships based on military and economic cooperation have been severed in recent years; thus, it supports a general balancing behavior. Findings also suggest that a specific group of countries subscribe to new opportunistic and defensive bandwagoning by embarking on talks and partnerships in the fields of health and science, regardless of the sanction regime, signaling defiance against Western- led world order

Failure to relaunch? The United States, nuclear North Korea, and the future of the six-party talks

During the past twenty years, Washington has oscillated between tentative engagement with Pyongyang under the Clinton administration and isolation and multilateralism under the Bush administration. With the Obama administration almost nearing its four-year tenure, the Six-Party Talks have stalled and North Korea's multiple attacks on the South in 2010 have created new instabilities. Why so little results despite promises of a radical departure away from the Axis of Evil rhetoric and hard-line politics? This paper suggests that the Obama administration has utilized approaches that no longer fit current circumstances and hence failed to create an original, coherent and effective foreign policy

Physicochemical and bilogical characterization of soils from the vicinity of the Arctowski Polish Antarctic Station

Soil samples collected in 2006 from 4 different sites (Puchalski Hill and a moraine below this hill, an elephant seal colony and a penguin rookery) in the vicinity of Arctowski Polish Antarctic Station at King George Island were characterized in terms of physicochemical properties (pH, humidity, concentration of selected inorganic and organic substances), microbial colonization and the overall activity of selected enzymes (differentglycosidases and esterases). Activity of the latter enzymes was assayed by p-nitrophenyl and 4-methylumbelliferone derivatives of fatty acids (by spectrophotometric and fluorimetric method, respectively). The highest lipolytic activity was found in soils from the elephant seal colony and penguin rookery