Distance Problem Research Articles

On Ill-Posedness of Nonparametric Instrumental Variable Regression With Convexity Constraints

This note shows that adding monotonicity or convexity constraints on the regression function does not restore well-posedness in nonparametric instrumental variable regression. The minimum distance problem without regularisation is still locally ill-posed.

Virtual cluster optimisation for MapReduce-like applications

Infrastructure-as-a-service clouds are becoming ubiquitous for provisioning virtual machines on demand. Cloud service providers expect to use the least resources to deliver the best services. As users frequently request virtual machines to build virtual clusters and run MapReduce-like jobs for big data processing, cloud service providers intend to optimise the virtual cluster to minimise network latency and subsequently reduce data movement cost. In this paper, we focus on the virtual machine placement issue for provisioning virtual clusters with minimum network latency in clouds. We define the distance as the latency between virtual machines and use it to measure the affinity of a virtual cluster. Such metric of distance indicates the considerations of virtual machine placement and the topology of physical nodes in clouds. Then, we formulate our problem as the classical shortest distance problem and solve it by building an integer programming model. A greedy virtual machine placement algorithm is designed to get a compact virtual cluster. Furthermore, an improved heuristic algorithm is also presented for achieving a global resource optimisation. The simulation results verify our algorithms and the experiment results validate the improvement achieved by our approaches.

The Uneven Citizenry of Photography: Reading The “Political Ontology” of Photography from Southern Africa

The Uneven Citizenry of PhotographyReading The “Political Ontology” of Photography from Southern Africa Patricia Hayes (bio) Nothing is more timely than the argument that we should revisit the relationship between the viewer and the photographed event (Azoulay 2012). It signals that theorization and critique around photography is entering new ground. It is a long time since Sontag virtually paralyzed readers with the violence of her language around the taking of pictures (“shooting and shooting”), followed by her meditations “regarding the pain of others” (1977; 2003). Solomon Godeau’s more subtle and considered essay on documentary photography also highlighted the problem of a double distance: the distance between the photographed and the photographer, and the distance between the photographed and the viewer (180). One understands that these distances could reflect socioeconomic difference of class, national or global positionings of privilege or militarism, or lack of affinities arising from race, gender, religion, or age. It is therefore enormously attractive to consider the possibility that the viewer’s distance from the scene in an image might actually hold the potential of something positive instead of negative. Writing from the southern parts of Africa, and burdened by the formulations around the multiple historical disempowerments of Africans in the face of the camera, Azoulay’s argument on first reading seems to augur an exciting new opening for reading photographs. My purpose in this essay is modest. Prompted by a set of large propositions put forward by Ariella Azoulay in Civil Imagination: A Political Ontology of Photography, I hope to initiate a conversation regarding new claims around photography and to explore their implications based on layers of alternative research from southern Africa. I should start by saying that the prospects of shifting the discussion [End Page 173] from the confines of the art disciplines are potentially very liberating. Specifically, debates on South African photography have been very deeply affected by a move away from “documentary” as part of a transition away from the apartheid and anti-apartheid movements. Part of the problem is the ongoing belief and investment in the very notion of genre, and the need for artists and art historians to define new work against what is often a straw man constructed out of reductive examples of anti-apartheid photojournalism as “documentary” (Garb; Van Robbroeck). In South Africa this has produced a gulf between “then and now” that has left a massive imprint on ongoing aesthetic and political dynamics, and often creates the impression that politics was something in the anti-apartheid then, and a more aesthetic regime is of the post-apartheid now.1 A period of post-apartheid denigration of documentary has meant the dismissal of large bodies of complex and subtle extant work to the extent that many photographers for many years did not even develop films from the politicized 1980s because of a prevailing discourse against “bad” or “repetitious” photographs of historical passages, such as mass funerals. One of the virtues of Azoulay’s book, therefore, is that it points to the really critical potential lying in neglected archives of historical photographs and now-unfashionable bodies of overlooked work that cannot even find a home. Thus in the first instance, the very fact that Azoulay uses a wide range of photographs without prejudice and without genuflecting to genre is invigorating. New ideas can then gather around them, it seems, instead of anxiously conformist and disciplinary ones. In Civil Imagination Azoulay emphasizes the need to get away from a prevailing focus on the image narrowly linked to the photographer or producer. In brief, and at risk of reducing the intricacy and cohesion of these interlinked arguments, the author proposes that the situation around the taking of the photograph (the event of photography) should be rethought to consider what lies beyond the immediate frame of the image. Photography is much more than the pressing of the shutter button on a scene: all those participating in the scene enter a new world, even if the photograph is not taken. This world does not end when the photograph is taken. Azoulay then argues that a “civil imagination” can be triggered or activated for all those who view the image thereafter in response to...

On the distribution of cycles and paths in multichromosomal breakpoint graphs and the expected value of rearrangement distance.

Finding the smallest sequence of operations to transform one genome into another is an important problem in comparative genomics. The breakpoint graph is a discrete structure that has proven to be effective in solving distance problems, and the number of cycles in a cycle decomposition of this graph is one of the remarkable parameters to help in the solution of related problems. For a fixed k, the number of linear unichromosomal genomes (signed or unsigned) with n elements such that the induced breakpoint graphs have k disjoint cycles, known as the Hultman number, has been already determined. In this work we extend these results to multichromosomal genomes, providing formulas to compute the number of multichromosal genomes having a fixed number of cycles and/or paths. We obtain an explicit formula for circular multichromosomal genomes and recurrences for general multichromosomal genomes, and discuss how these series can be used to calculate the distribution and expected value of the rearrangement distance between random genomes.

KnowSim: A Document Similarity Measure on Structured Heterogeneous Information Networks.

As a fundamental task, document similarity measure has broad impact to document-based classification, clustering and ranking. Traditional approaches represent documents as bag-of-words and compute document similarities using measures like cosine, Jaccard, and dice. However, entity phrases rather than single words in documents can be critical for evaluating document relatedness. Moreover, types of entities and links between entities/words are also informative. We propose a method to represent a document as a typed heterogeneous information network (HIN), where the entities and relations are annotated with types. Multiple documents can be linked by the words and entities in the HIN. Consequently, we convert the document similarity problem to a graph distance problem. Intuitively, there could be multiple paths between a pair of documents. We propose to use the meta-path defined in HIN to compute distance between documents. Instead of burdening user to define meaningful meta-paths, an automatic method is proposed to rank the meta-paths. Given the meta-paths associated with ranking scores, an HIN-based similarity measure, KnowSim, is proposed to compute document similarities. Using Freebase, a well-known world knowledge base, to conduct semantic parsing and construct HIN for documents, our experiments on 20Newsgroups and RCV1 datasets show that KnowSim generates impressive high-quality document clustering.

A group-theoretic viewpoint on Erdős–Falconer problems and the Mattila integral

We obtain nontrivial exponents for Erdős–Falconer type point configuration problems. Let T_k(E) denote the set of distinct congruent k -dimensional simplices determined by (k+1) -tuples of points from E . For 1 \le k \le d , we prove that there exists a t_{k,d} < d such that, if E \subset {\mathbb R}^d , d \ge 2 , with \mathrm {dim}_{{\mathcal H}}(E)>t_{k,d} , then the {k+1 \choose 2} -imensional Lebesgue measure of T_k(E) is positive. Results of this type were previously obtained for triangles in the plane (k=d=2) in [8] and for higher k and d in [7]. We improve upon those exponents, using a group action perspective, which also sheds light on the classical approach to the Falconer distance problem.

On the Minkowski distances and products of sum sets

Given two points p, q in the real plane, the signed area of the rectangle with the diagonal [pq] equals the square of the Minkowski distance between the points p, q. We prove that N >1 points in the Minkowski plane ℝ1,1 generate \(\Omega (\frac{N}{{\log N}})\) distinct distances, or all the distances are zero. The proof follows the lines of the Elekes/Sharir/Guth/Katz approach to the Erdős distance problem, analysing the 3D incidence problem, arising by considering the action of the Minkowski isometry group ISO*(1, 1).

Paternal Instincts

Paternal Instincts

Cultural distance and emotional problems among immigrant and refugee youth in Canada: Findings from the New Canadian Child and Youth Study (NCCYS)

This study examines the widely accepted but under-studied proposition that the greater the cultural distance (CD) between home country and country of resettlement the greater the mental health risk for immigrant and refugee youth. The study also explores pathways through which CD, a macro-social stressor, might exert its mental health effect through meso-environmental stressors including poverty and discrimination, as well as micro-environmental familial stressors. Acculturation strategies and personal competencies are also examined as sources of resilience. The study sample consists of 2074 immigrant and refugee girls and boys, ages 11–13, belonging to 16 different ethnocultural communities, and living in six different Canadian cities. Study data consist of interviews with youth and with the parent deemed the most knowledgeable. Results reveal that CD did adversely affect youth mental health but the effect was relatively small. Family environment variables, particularly parental depression and harsh parenting, accounted for about one third of the effect of CD. Parents in ethnocultural communities that were culturally distant from Canada were more likely to employ harsh parenting practices than parents coming from culturally closer countries. Immigrant youth from culturally distant backgrounds were more likely to perceive discrimination than youth from culturally closer backgrounds. Social competence had an inverse relationship with emotional symptoms. An integration style of acculturation was more advantageous than an isolated, assimilated or marginalized style. The longer youth from culturally distant backgrounds lived in Canada, the worse their mental health tended to be: for youth from culturally closer backgrounds, the opposite was true. The discussion addresses implications for resettlement interventions and policy.

A Dynamic Programming Algorithm For (1,2)-Exemplar Breakpoint Distance.

The exemplar breakpoint distance problem is motivated by finding conserved sets of genes between two genomes. It asks to find respective exemplars in two genomes to minimize the breakpoint distance between them. If one genome has no repeated gene (called trivial genome) and the other has genes repeating at most twice, it is referred to as the (1, 2)-exemplar breakpoint distance problem, EBD(1, 2) for short. Little has been done on algorithm design for this problem by now. In this article, we propose a parameter to describe the maximum physical span between two copies of a gene in a genome, and based on it, design a fixed-parameter algorithm for EBD(1, 2). Using a dynamic programming approach, our algorithm can take O(4(s)n(2)) time and O(4(s)n) space to solve an EBD(1, 2) instance that has two genomes of n genes where the second genome has each two copies of a gene spanning at most s copies of the genes. Our algorithm can also be used to compute the maximum adjacencies between two genomes. The algorithm has been implemented in C++. Simulations on randomly generated data have verified the effectiveness of our algorithm. The software package is available from the authors.

A contribution to the Aleksandrov conservative distance problem in two dimensions

Let E be a two-dimensional real normed space. In this paper we show that if the unit circle of E does not contain any line segment such that the distance between its endpoints is greater than 1, then every transformation ϕ:E→E which preserves the unit distance is automatically an affine isometry. In particular, this condition is satisfied when the norm is strictly convex.

التعلیم عن بعد وشبکات التواصل الاجتماعى

The educational systems currently witness massive changes on all levels: visions, goals and methods. With continuous growth in social and economic plans of countries and the need for putting such plans into force through high quality educational outcomes, the directions towards developing education and supporting learners are on increase not only for gaining knowledge or gathering information but also for developing the skills prerequisite for mixing with the society. In order to improve the educational production, the educators resort to integrate technology in education and develop the traditional methods in a way that contributes to emergence of newfangled methods such as the distance learning which provides learning opportunities for all society classes with whatever circumstances and multiple needs. Furthermore, this type of learning requires utilizing the modern communication technology and its methods in order to overcome the distance problem between the teacher and the learner like the internet. Internet possesses multiple applications which become pioneering ones in the distance learning field; due to the fact that it constitutes an effective communication method between the teacher and the learner on the one hand and between the learners and his/ her peers on the other hand. In addition the teacher and the learning can obtain feedback from the other partner. Recently, social networks have emerged on the Internet and spread on a large scale internationally. Moreover, such social networks become the most internationally visited sites to the extent that they become the third in order of priority after home and work or school or university for the human to resort to and in his/ her point of view, such social networks are deemed one of the most robust methods of distance learning second generation which determine the cooperative learning and the community participation as a main educational goal together with the behavioral and cognitive goals in the contemporary educational systems. Currently, the most important question is as follows: how can learning types be developed to enable the learner to build knowledge in the cooperative learning system where the learner shares such knowledge with other members of the society? Our relationship with the knowledge has changed in this age; because it has shifted from a single perspective providing the knowledge in a narrow template surrounded with restrictions and readymade frameworks to multiple dynamic interactions. The current paper seeks to identify the impact of using the social networks on the distance learning through shedding much light on the distance learning concepts, distance learning benefits as well as the social networks represented in Facebook, Twitter and Youtube.

Analysis on Free Video Call Applications Reliability as a Tool a case study of Online Islamic Matrimony

The internet era has been improved so much over this past decade; wherepeople can easily get connected without having to consider distancebetween different locations. The way people communicate also haschanged from texting using conventional letter or SMS, to audio usingphone call and now video call where we can see and hear the person whowe talk to. Due to distance problem, nowadays some people prefer to useOnline Video Call to perform weddings. Although some Moslems are stilldebating the validity of an online matrimony where some Islamic scholarsagree by considering certain condition while some others disagree, thispaper won’t be discussing about the debated issue. This paper will only befocused on the video call application reliability in order to have a validonline Islamic matrimony. The comparison will be using free video callapplications such as Skype, Google Hang-out and Facebook Video Call

Suppression distance computation for hierarchical clusterings

We discuss the computation of a distance between two hierarchical clusterings of the same set. It is defined as the minimum number of elements that have to be removed so the remaining clusterings are equal. The problem of distance computing was extensively studied for partitions. We prove it can be solved in polynomial time in the case of hierarchies as it gives birth to a class of perfect graphs. We also propose an algorithm based on recursively computing maximum assignments.

Why Do Women Deliver at Home? Multilevel Modeling of Ethiopian National Demographic and Health Survey Data

BackgroundDespite of the existing intensive efforts to improve maternal health in Ethiopia, the proportion of birth delivered at home remains high and is still the top priority among the national health threats.ObjectiveThe study aimed to examine effects of individual women and community-level factors of women’s decision on place of delivery in Ethiopia.MethodsData were obtained from the nationally representative 2011 Ethiopian Demographic and Health Survey (EDHS) which used a two-stage cluster sampling design with rural-urban and regions as strata. The EDHS collected data from a big sample size but our study focused on a sample of 7,908 women whose most recent birth was within five years preceding 2011 and 576 communities in which the women were living in. The data were analyzed using a two-level mixed-effects logistic regression to determine fixed-effects of individual- and community-level factors and random-intercept of between-cluster characteristics.ResultsIn the current study, 6980 out of 7908 deliveries (88.3%) took place at home. Lower educational levels (OR=2.74, 95%CI:1.84,4.70; p<0.0001), making no or only a limited number of ANC visits (OR=3.72,95%CI:2.85, 4.83; p<0.0001), non-exposure to media (OR=1.51, 95%CI 1.13, 2.01; p=0.004), higher parity (OR=2.68, 95%CI:1.96,3.68; p<0.0001), and perceived distance problem to reach health facilities (OR=1.29, 95%CI:1.03,1.62; p=0.022) were positively associated with home delivery. About 75% of the total variance in the odds of giving birth at home was accounted for the between-community differences of characteristics (ICC=0.75, p<0.0001). With regard to community-level characteristics, rural communities (OR=4.67, 95%CI:3.06,7.11; p<0.0001), pastoralist communities (OR=4.53, 95%CI:2.81,7.28; p<0.0001), communities with higher poverty levels (OR=1.49 95%CI:1.08,2.22; p=0.048), with lower levels of ANC utilization (OR=2.01, 95%CI:1.42,2.85; p<0.0001) and problem of distance to a health facility (OR=1.29, 95%CI:1.03,1.62; p=0.004) had a positive influence on women to give birth at home.ConclusionsNot only individual characteristics of women, but also community-level factors determine women’s decision to deliver at home.

Penerapan Metode Hill Climbing Pada Sistem Informasi Geografis Untuk Mencari Lintasan Terpendek

Heuristic search methods is one of the methods commonly in use in finding the shortest path, one of which, namely the methods Hill Climbing process where testing is done using heuristic functions. Problems generally encountered is the shortest path search to solve the problem of distance can be changed into a graph structure, where the point of declaring the city and the State line that connects the two cities. From the logic so that it can locate destinations and save on travel costs. The hallmarks of this algorithm are all possible solutions will have then checked one by one from the left side, so it will be obtained solutions with optimal results. On a Hill Climbing method according to case using geographic information systems as a tool in making a decision, by way of collect, examine, and analyze information related to digital map. with a combination of Hill Climbing method and geographic information systems can result in an application that is certainly feasible for use in the search path problems. Keywords : Hill Climbin method; digital map; Geographic Information Systems

On the family-free DCJ distance and similarity.

Structural variation in genomes can be revealed by many (dis)similarity measures. Rearrangement operations, such as the so called double-cut-and-join (DCJ), are large-scale mutations that can create complex changes and produce such variations in genomes. A basic task in comparative genomics is to find the rearrangement distance between two given genomes, i.e., the minimum number of rearragement operations that transform one given genome into another one. In a family-based setting, genes are grouped into gene families and efficient algorithms have already been presented to compute the DCJ distance between two given genomes. In this work we propose the problem of computing the DCJ distance of two given genomes without prior gene family assignment, directly using the pairwise similarities between genes. We prove that this new family-free DCJ distance problem is APX-hard and provide an integer linear program to its solution. We also study a family-free DCJ similarity and prove that its computation is NP-hard.

Characteristic of wireless power transmission S-Parameter for a superconductor coil

Many studies are being conducted to implement wireless charging, for example, for cellular phones or electronic tooth brushes, via wireless power transmission technique. However, the magnetic induction method had a very short transmission distance. To solve this problem, the team of Professor Marin Soljacic proposed a magnetic resonance system that used two resonance coils with the same resonance frequency. It had an approximately 40% efficiency at a 2m distance. The system improved the low efficiency and short distance problems of the existing systems. So it could also widen the application range of wireless power transmission. Many studies on the subject are underway. In this paper, the superconductor coil was used to improve the efficiency of magnetic resonance wireless power transmission. The resonance wireless power transmission system had a source coil, a load coil, and resonance coils (a transmitter and a receiver). The efficiency and distance depended on the characteristics of the transmitter and receiver coils that had the same resonance frequency. Therefore, two resonance coils were fabricated by superconductors. The current density of the superconductor was higher than that of the normal conductor coil. Accordingly, it had a high quality-factor and improved efficiency.

Operator norm attainment and Birkhoff–James orthogonality

Recently in [Sain D., Paul K., Operator norm attainment and inner product spaces, Linear Algebra Appl. 439 (2013) 2448–2452] it was proved that if T is a linear operator on a finite dimensional real normed linear space X such that T attains norm only on ±D, where D is a connected closed subset of SX, then T satisfies the Bhatia–Šemrl (BŠ) property [Bhatia R., Šemrl P., Orthogonality of matrices and distance problem, Linear Algebra Appl. 287 (1999) 77–85], i.e., for A∈L(X), T⊥BA implies that there exists x∈D such that Tx⊥BAx. Here we explore the converse of the above result. We prove that in a real normed linear space X of dimension 2, a linear operator T satisfies the BŠ property if and only if the set of unit vectors on which T attains norm is connected in the corresponding projective space RP1≡SX/{x∼−x}. Motivated by the result in 2 dimensions, we conjecture that this characterization of BŠ property is true in general n-dimensional real normed linear spaces. We further prove that if the space X is strictly convex, then the set of operators in L(X) which satisfy the BŠ property is dense in L(X).

Accurate and robust adaptive mesh refinement for aerodynamic simulation with multi‐block structured curvilinear mesh

SummaryA multi‐block curvilinear mesh‐based adaptive mesh refinement (AMR) method is developed to satisfy the competing objectives of improving accuracy and reducing cost. Body‐fitted curvilinear mesh‐based AMR is used to capture flow details of various length scales. A series of efforts are made to guarantee the accuracy and robustness of the AMR system. A physics‐based refinement function is proposed, which is proved to be able to detect both shock wave and vortical flow. The curvilinear mesh is refined with cubic interpolation, which guarantees the aspect ratio and smoothness. Furthermore, to enable its application in complex configurations, a sub‐block‐based refinement strategy is developed to avoid generating invalid mesh, which is the consequence of non‐smooth mesh lines or singular geometry features. A newfound problem of smaller wall distance, which negatively affects the stability and is never reported in the literature, is also discussed in detail, and an improved strategy is proposed. Together with the high‐accuracy numerical scheme, a multi‐block curvilinear mesh‐based AMR system is developed. With a series of test cases, the current method is verified to be accurate and robust and be able to automatically capture the flow details at great cost saving compared with the global refinement. Copyright © 2015 John Wiley &amp; Sons, Ltd.