Stable and Efficient Structures for the Content Production and Consumption in Information Communities

Real-world information communities exhibit inherent structures that characterize a system that is stable and efficient for content production and consumption. In this paper, we study such structures through mathematical modelling and analysis. We formulate a generic model of a community in which each member decides how they allocate their time between content production and consumption with the objective of maximizing their individual reward. We define the community system as "stable and efficient" when a Nash equilibrium is reached while the social welfare of the community is maximized. We investigate the conditions for forming a stable and efficient community under two variations of the model representing different internal relational structures of the community. Our analysis results show that the structure with "a small core of celebrity producers" is the optimally stable and efficient for a community. These analysis results provide possible explanations to the sociological observations such as "the Law of the Few" and also provide insights into how to effectively build and maintain the structure of information communities.Comment: 21 page

Quantum Speed Limit for Perfect State Transfer in One Dimension

The basic idea of spin chain engineering for perfect quantum state transfer (QST) is to find a set of coupling constants in the Hamiltonian, such that a particular state initially encoded on one site will evolve freely to the opposite site without any dynamical controls. The minimal possible evolution time represents a speed limit for QST. We prove that the optimal solution is the one simulating the precession of a spin in a static magnetic field. We also argue that, at least for solid-state systems where interactions are local, it is more realistic to characterize the computation power by the couplings than the initial energy.Comment: 5 pages, no figure; improved versio

Epic Human Failure on June 30, 2013

Nineteen Prescott Fire Department, Granite Mountain Hot Shot (GMHS) wildland firefighters and supervisors (WFF), perished on the June 2013 Yarnell Hill Fire (YHF) in Arizona. The firefighters left their Safety Zone during forecast, outflow winds, triggering explosive fire behavior in drought-stressed chaparral. Why would an experienced WFF Crew, leave ‘good black’ and travel downslope through a brush-filled chimney, contrary to their training and experience? An organized Serious Accident Investigation Team (SAIT) found, “… no indication of negligence, reckless actions, or violations of policy or protocol.” Despite this, many WFF professionals deemed the catastrophe, “… the final, fatal link, in a long chain of bad decisions with good outcomes.” This paper is a theoretical and realistic examination of plausible, faulty, human decisions with prior good outcomes; internal and external impacts, influencing the GMHS; and two explanations for this catastrophe: Individual Blame Logic and Organizational Function Logic, and proposed preventive mitigations

Effective non-Markovian description of a system interacting with a bath

We study a harmonic system coupled to chain of first neighbor interacting oscillators. After deriving the exact dynamics of the system, we prove that one can effectively describe the exact dynamics by considering a suitable shorter chain. We provide the explicit expression for such an effective dynamics and we provide an upper bound on the error one makes considering it instead of the dynamics of the full chain. We eventually prove how error, timescale and number of modes in the truncated chain are related

Teachers’ Perceptions on the Relationship Between Teachers’ Working Conditions and Pupils’ Reading Ability in Pre-Primary Schools in Nakuru County, Kenya

One of the most important factors in realizing reading as a subject in pre-primary schools is teacher working conditions. Literature suggests that working conditions are crucial in teaching of reading and pupils’ reading ability. However, empirical studies that have examined pupils’ reading ability have not focused on the relationship between teacher working conditions and reading ability. Further, the few empirical studies that have examined the relationships have been conducted in primary and secondary schools. Whereas most pre-primary school teachers in Kenya work under unfavourable conditions, past studies have not examined the relationship between working conditions and reading ability of pre-primary school pupils in Kenya. The purpose of this study was to examine the relationship between teacher working conditions and pupils’ reading ability. The study was based on Herzberg’s two factor theory. The study adopted a correlational research design. The target population for the study was 79 head teachers and 79 pre-primary 2 class teachers in public schools in Rongai Sub-County Nakuru. A stratified sample of pre-primary schools in the four zones in Rongai Sub-county was used for the study. The sample size comprised of 66 head teachers and 66 pre-primary 2 teachers. The questionnaires were used to collect data from respondents.. Data was summarized using descriptive statistics such as frequencies, means and standard deviations. To test the hypotheses, Pearson’s Product-moment correlation coefficient was used. The results revealed that there was a relationship between teacher workload, school leadership and pupils’ reading ability. The study concludes that teacher workload and school leadership affect the reading ability of pre-primary school pupils. The study recommends that to improve reading ability, school management should provide effective school leadership and ensure that pre-primary school classes are of reasonable sizes so that teachers do not have a heavy workload. Keywords: Working Conditions, Teacher Workload, School Leadership, Reading Ability; Pre-primary School Pupils DOI: 10.7176/JEP/10-18-23 Publication date:June 30th 201

How to construct spin chains with perfect state transfer

It is shown how to systematically construct the $XX$ quantum spin chains with nearest-neighbor interactions that allow perfect state transfer (PST). Sets of orthogonal polynomials (OPs) are in correspondence with such systems. The key observation is that for any admissible one-excitation energy spectrum, the weight function of the associated OPs is uniquely prescribed. This entails the complete characterization of these PST models with the mirror symmetry property arising as a corollary. A simple and efficient algorithm to obtain the corresponding Hamiltonians is presented. A new model connected to a special case of the symmetric $q$-Racah polynomials is offered. It is also explained how additional models with PST can be derived from a parent system by removing energy levels from the one-excitation spectrum of the latter. This is achieved through Christoffel transformations and is also completely constructive in regards to the Hamiltonians.Comment: 7 page

An Intra-Bone Axial Load Transducer: Development and Validation in an In-Vitro Radius Model

Background Accurate measurement of forces through the proximal radius can assess the effects of some surgical procedures on radioulnar load sharing, but is difficult to achieve given the redundant loading nature of the musculoskeletal system. Previously reported devices have relied on indirect measurements that may alter articular joint location and function. An axial load transducer interposed in the diaphysis of the radius may accurately quantify unknown axial loads of the proximal radius, and maintain articular location. Methods An in-vitro radius model was developed by interposing an axial load transducer in the diaphysis of the proximal radius. Static loads of 20, 40, 60, 80, and 100 N were applied with a servo-hydraulic actuator to the native radial head at angles of 10°, 20°, 30°, and 40° in the anterior, posterior, medial and lateral directions. Findings Linear regression of five repeatability trials showed excellent agreement between the transducer and applied loads (R 2 = 1 for all trials). For off-axis net joint loads, the majority of measured loading errors were within the inter-quartile range for mean loads up to 80 N. Loads below 80 N and outside the inter-quartile range had errors of less than 1 N. Conclusions The repeatability and off-axis net joint load results of this study validate the effectiveness of the interposed axial load transducer to accurately quantify proximal radius loads. The surgical technique preserves the native articular location and soft-tissue constructs, like the annular ligament. The modular design allows for testing the effects of length-changing osteotomies in subsequent biomechanical studies

Perfect State Transfer, Effective Gates and Entanglement Generation in Engineered Bosonic and Fermionic Networks

We show how to achieve perfect quantum state transfer and construct effective two-qubit gates between distant sites in engineered bosonic and fermionic networks. The Hamiltonian for the system can be determined by choosing an eigenvalue spectrum satisfying a certain condition, which is shown to be both sufficient and necessary in mirror-symmetrical networks. The natures of the effective two-qubit gates depend on the exchange symmetry for fermions and bosons. For fermionic networks, the gates are entangling (and thus universal for quantum computation). For bosonic networks, though the gates are not entangling, they allow two-way simultaneous communications. Protocols of entanglement generation in both bosonic and fermionic engineered networks are discussed.Comment: RevTeX4, 6 pages, 1 figure; replaced with a more general example and clarified the sufficient and necessary condition for perfect state transfe

Evolutionary Agent-Based Simulation of the Introduction of New Technologies in Air Traffic Management

Accurate simulation of the effects of integrating new technologies into a complex system is critical to the modernization of our antiquated air traffic system, where there exist many layers of interacting procedures, controls, and automation all designed to cooperate with human operators. Additions of even simple new technologies may result in unexpected emergent behavior due to complex human/ machine interactions. One approach is to create high-fidelity human models coming from the field of human factors that can simulate a rich set of behaviors. However, such models are difficult to produce, especially to show unexpected emergent behavior coming from many human operators interacting simultaneously within a complex system. Instead of engineering complex human models, we directly model the emergent behavior by evolving goal directed agents, representing human users. Using evolution we can predict how the agent representing the human user reacts given his/her goals. In this paradigm, each autonomous agent in a system pursues individual goals, and the behavior of the system emerges from the interactions, foreseen or unforeseen, between the agents/actors. We show that this method reflects the integration of new technologies in a historical case, and apply the same methodology for a possible future technology

Inverse eigenvalue problem for discrete three-diagonal Sturm-Liouville operator and the continuum limit

In present article the self-contained derivation of eigenvalue inverse problem results is given by using a discrete approximation of the Schroedinger operator on a bounded interval as a finite three-diagonal symmetric Jacobi matrix. This derivation is more correct in comparison with previous works which used only single-diagonal matrix. It is demonstrated that inverse problem procedure is nothing else than well known Gram-Schmidt orthonormalization in Euclidean space for special vectors numbered by the space coordinate index. All the results of usual inverse problem with continuous coordinate are reobtained by employing a limiting procedure, including the Goursat problem -- equation in partial derivatives for the solutions of the inversion integral equation.Comment: 19 pages There were made some additions (and reformulations) to the text making the derivation of the results more precise and understandabl