Zigzag Path Research Articles

Synergy of multi-scale toughening and protective mechanisms at hierarchical branch-stem interfaces.

Biological materials possess a variety of artful interfaces whose size and properties are adapted to their hierarchical levels and functional requirements. Bone, nacre, and wood exhibit an impressive fracture resistance based mainly on small crystallite size, interface organic adhesives and hierarchical microstructure. Currently, little is known about mechanical concepts in macroscopic biological interfaces like the branch-stem junction with estimated 1014 instances on earth and sizes up to few meters. Here we demonstrate that the crack growth in the upper region of the branch-stem interface of conifer trees proceeds along a narrow predefined region of transversally loaded tracheids, denoted as sacrificial tissue, which fail upon critical bending moments on the branch. The specific arrangement of the tracheids allows disconnecting the overloaded branch from the stem in a controlled way by maintaining the stem integrity. The interface microstructure based on the sharply adjusted cell orientation and cell helical angle secures a zig-zag crack propagation path, mechanical interlock closing after the bending moment is removed, crack gap bridging and self-repairing by resin deposition. The multi-scale synergetic concepts allows for a controllable crack growth between stiff stem and flexible branch, as well as mechanical tree integrity, intact physiological functions and recovery after the cracking.

Strategic switchbacks: Dynamic commercialization strategies for technology entrepreneurs

We present a synthetic framework in which a technology entrepreneur employs a dynamic commercialization strategy to overcome obstacles to the adoption of the firm’s ideal strategy. Whereas prior work portrays the choice of whether to license a new technology or to self-commercialize as a single, static decision, we suggest that when entrepreneurs encounter obstacles to their ideal strategy they can nevertheless achieve it by temporarily adopting a non-ideal strategy. We refer to the sequential implementation of commercialization strategies, in which the first strategy enables the second, as a switchback—reminiscent of zigzag paths that enable passage up steep mountains. We analyze conditions under which switchbacks can be effective in enabling the entrepreneur’s ideal commercialization strategy given the attending costs, risks, and likely incumbent response.

Morphometric Study of the Mare Oviductal Mucosa at Different Reproductive Stages

The objectives of this work were to describe some morphometric characteristics and to establish quantitative parameters of different regions of the equine oviductal mucosa from the isthmus, ampullary-isthmic junction (AIJ), and ampulla. Twenty-one mixed-bred mares were used for this study. Mares were selected in the following reproductive phases: anestrus, estrus, and diestrus. The left oviducts were examined with light microscopy, and rights ones were studied through the intraoviductal molds. The isthmus showed the smallest luminal area, mucosal area, epithelial perimeter, and luminal diameter. On the molds surfaces, some grooves extended as longitudinal canals, reducing their depth as they approached to the AIJ. Several small height projections, some obliquely positioned towards utero-tubal junction, were observed in all reproductive phases. These formations may represent pockets or cul-de-sacs in the basal areas of the epithelial folds. The AIJ mucosa gradually changed from the smooth isthmic region toward highly folded ampulla. The number and complexity of epithelial folds showed moderate increase in the same way that many of the morphometric parameters. Multiple curves were observed on the molds of the AIJ, creating a zigzag path in the oviductal lumen. In the ampulla, the high branched epithelial folds occupied most of the lumen, leaving a small luminal area free. A linear relationship between epithelial perimeter and mucosal area was found. The presence of glandular-like structures was observed in all the reproductive stages studied. The equine endosalpinx reveals a highly complex tridimensional arrangement where each region shows very particular and specific designs.

3D simulation of short fatigue crack propagation by finite element crystal plasticity and remeshing

An iterative method to simulate 3D fatigue crack propagation in crystalline materials is proposed and demonstrated on simple test cases. The method relies on the computation of a damage indicator based on plastic activity around the crack tip. By post-processing this quantity after a given loading sequence, local crack direction and growth rate are estimated along the crack path. Dedicated remeshing routines allow the crack to propagate in 3D and the iterative process can continue with the updated crack geometry. Two examples in a BCC single crystal featuring different slip systems demonstrate the crack propagation simulations under cyclic loading over distances comparable to the crystal size and with non-regular crack shapes such as zig-zag crack paths. The effect of transferring plastic fields between propagation steps is also analysed.

A Colour Image Encryption Scheme Using Permutation-Substitution Based on Chaos

An encryption scheme for colour images using a spatiotemporal chaotic system is proposed. Initially, we use the R, G and B components of a colour plain-image to form a matrix. Then the matrix is permutated by using zigzag path scrambling. The resultant matrix is then passed through a substitution process. Finally, the ciphered colour image is obtained from the confused matrix. Theoretical analysis and experimental results indicate that the proposed scheme is both secure and practical, which make it suitable for encrypting colour images of any size.

Testing The Healing Environment Conditions for Nurses with two Independent Variables: Visibility Enhancement along with Shortening the Walking Distance of the Nurses to Patient - Focused on LogWare stop sequence and space syntax for U-Shape, L- Shape and I-Shape NS-

Purpose: Maximizing human comfort in design of medical environments depends immensely on specialized architects particularly critical care design; the study proposes Evidence-Based Design as an apparent analog to Evidence-Based Medicine. Healthcare facility designs are substantially based on the findings of study in an effort to design environments that augment care by improving patient safety and being therapeutic. On SPSS (Statistical Package for Social Science) t-test is applied to simulate two independent variables of PDR (Pre Design-Research) and POE (Post- Occupancy Evaluation). PDR is conducted on relatively new hospital Hallym University Dongtan Sacred Heart Hospital to analyse visibility from researchers' point of view, here the ICU is arranged in I-Shape. POE is applied on Dongguk University Ilsan Hospital to simulate walking on LogWare where two NS are designed based on L- Shape and Seoul St. Mary's Hospital, The Catholic University of Korea where five NS are functional for ICU Intensive Care Unit, Surgical Intensive Care Unit (SICU), Medical Intensive Care Unit (MICU), Critical Care Unit (CCU), Korean Oriental Medical Care Unit which are mostly arranged in U-Shape, and walking pattern is recognized to be in a zigzag path. Method: T-Test is applied on two dependent communication variables: walkability and visibility, with confidence interval of 95%. This study systematically analyses the Nurse Station (NS) typo-morphology, and simulates nurse horizontal circulation, by computing round route visits to patient's bed, then estimating minimum round route on LogWare stop sequence software. The visual connectivity is measured on depth map graphs. Hence the aim is to reduce staff stress and fatigue for better patients care by minimizing staff horizontal travel time and to facilitate nurse walk path and support space distribution by increasing effectiveness in delivering care. Result: Applying visibility graph and isovist field on space syntax on I- Shape, L- Shape and U- Shape ICU (SICU, MICU and CCU) configuration, I-shape facilitated 20% more patients in linear view as they stir to rise from their beds from nurse station compared to U-shape. In conclusion, it was proved that U-Shape supply minimum walking and maximum visibility; and L shape provides just visibility as the nurse is at pivot. I shape provides panoramic view from the Nurse Station but very rigorous walking.

Fracture mechanics of monolayer molybdenum disulfide

Molecular dynamics (MD) modeling is used to study the fracture toughness and crack propagation path of monolayer molybdenum disulfide (MoS2) sheets under mixed modes I and II loading. Sheets with both initial armchair and zigzag cracks are studied. The MD simulations predict that crack edge chirality, tip configuration and the loading phase angle influence the fracture toughness and crack propagation path of monolayer MoS2 sheets. Furthermore, under all loading conditions, both armchair and zigzag cracks prefer to extend along a zigzag path, which is in agreement with the crack propagation path in graphene. A remarkable out-of-plane buckling can occur during mixed mode loading which can lead to the development of buckling cracks in addition to the propagation of the initial cracks.

Message Efficient Checkpointing and Rollback Recovery in Heterogeneous Mobile Networks

Heterogeneous networks provide an appealing way of expanding the computing capability of mobile networks by combining infrastructure-less mobile ad-hoc networks with the infrastructure-based cellular mobile networks. The nodes in such a network range from low-power nodes to macro base stations and thus, vary greatly in their capabilities such as computation power and battery power. The nodes are susceptible to different types of transient and permanent failures and therefore, the algorithms designed for such networks need to be fault-tolerant. The article presents a checkpointing algorithm for the rollback recovery of mobile hosts in a heterogeneous mobile network. Checkpointing is a well established approach to provide fault tolerance in static and cellular mobile distributed systems. However, the use of checkpointing for fault tolerance in a heterogeneous environment remains to be explored. The proposed protocol is based on the results of zigzag paths and zigzag cycles by Netzer–Xu. Considering the heterogeneity prevalent in the network, an uncoordinated checkpointing technique is employed. Yet, useless checkpoints are avoided without causing a high message overhead.

Interpretation of Fracture Toughness and R-Curve Behavior by Direct Observation of Microfracture Process in Ti-Based Dendrite-Containing Amorphous Alloys

Fracture properties of Ti-based amorphous alloys containing ductile β dendrites were explained by directly observing microfracture processes. Three Ti-based amorphous alloys were fabricated by adding Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy by a vacuum arc melting method. The effective sizes of dendrites varied from 63 to 104 μm, while their volume fractions were almost constant within the range from 74 to 76 pct. The observation of the microfracture of the alloy containing coarse dendrites revealed that a microcrack initiated at the amorphous matrix of the notch tip and propagated along the amorphous matrix. In the alloy containing fine dendrites, the crack propagation was frequently blocked by dendrites, and many deformation bands were formed near or in front of the propagating crack, thereby resulting in a zig-zag fracture path. Crack initiation toughness was almost the same at 35 to 36 MPa√m within error ranges in the three alloys because it was heavily affected by the stress applied to the specimen at the time of crack initiation at the crack tip as well as strength levels of the alloys. According to the R-curve behavior, however, the best overall fracture properties in the alloy containing fine dendrites were explained by mechanisms of blocking of the crack growth and crack blunting and deformation band formation at dendrites.

Study of Mesomorphism Through a Novel Homologous Series and Its Relation to Molecular Structure

A novel homologous series 4-(4′-n-alkoxy benzoyloxy)-3-chloro phenyl azo,3″,4″-dichlorobenzenes was synthesized with a view to understand and establish the relation between mesomorphism and the molecular structure. The novel series consists of 12 members, which showed commencement of monotropic nematic mesophase formation from the butoxy homologue and continued up to the hexadecyloxy homologue without exhibition of a smectic mesophase. The textures of the nematic mesophase are threaded or Schlieren in type. Transition temperatures were determined by an optical polarizing microscope equipped with a heating stage. Isotropic-nematic transition curve of the phase diagram behaved in normal manner with exhibition of odd-even effect. Solid-isotropic transition curve behaved descending tendency by adopting zigzag path up to the pentyloxy homologue; which include methoxy to propoxy homologues as nonmesomorphic derivatives. Thermal stability for the nematic is just a few degrees (1°C to 2°C). Analytical and spectral data support the molecular structures. The mesomorphic properties of present novel series are compared with structurally similar other known homologous series.

The East Anglia Road: The Zigzag Path of the Transformation of a Traditional English Agricultural Area

East Anglia, in the east of England, is a relatively independent geographical unit. As a traditional agricultural area that was relatively developed in medieval times, it had distinctive economic and social features that differed from those of typical feudal agricultural areas. In the process of Britain’s transformation from an agricultural society into an industrial one, East Anglia, on the basis of its own resources, traditions and strengths, kept exploring directions for the economic development of the region, following a zigzag path of “traditional agriculture→proto-industrialization→commercialized agriculture” and eventually finding the economic orientation that suited it. This process of the transformation of East Anglia reflects both the complexity of Britain’s rise and the diversity of paths from agricultural to industrial society.

Computational Approaches to Understanding the Role of Fibroblast-Myocyte Interactions in Cardiac Arrhythmogenesis.

The adult heart is composed of a dense network of cardiomyocytes surrounded by nonmyocytes, the most abundant of which are cardiac fibroblasts. Several cardiac diseases, such as myocardial infarction or dilated cardiomyopathy, are associated with an increased density of fibroblasts, that is, fibrosis. Fibroblasts play a significant role in the development of electrical and mechanical dysfunction of the heart; however the underlying mechanisms are only partially understood. One widely studied mechanism suggests that fibroblasts produce excess extracellular matrix, resulting in collagenous septa. These collagenous septa slow propagation, cause zig-zag conduction paths, and decouple cardiomyocytes resulting in a substrate for arrhythmia. Another emerging mechanism suggests that fibroblasts promote arrhythmogenesis through direct electrical interactions with cardiomyocytes via gap junctions. Due to the challenges of investigating fibroblast-myocyte coupling in native cardiac tissue, computational modeling and in vitro experiments have facilitated the investigation into the mechanisms underlying fibroblast-mediated changes in cardiomyocyte action potential morphology, conduction velocity, spontaneous excitability, and vulnerability to reentry. In this paper, we summarize the major findings of the existing computational studies investigating the implications of fibroblast-myocyte interactions in the normal and diseased heart. We then present investigations from our group into the potential role of voltage-dependent gap junctions in fibroblast-myocyte interactions.

Synthesis and Liquid Crystal Behavior of a Novel Ester Homologous Series

A novel ester homologous series of 4-[4’-n-alkoxy cinnamoyloxy] benzyl benzoates has been synthesized. The series consists of 12 homologues. Liquid crystal properties commence from the sixth member to the last member of the series with the exhibition of an enantiotropic nematic phase without the exhibition of any smectogenic mesophase. The remaining homologues do not exhibit liquid crystal behavior. The texture of the nematic phase is of the threaded or Schlieren type. The solid-nematic or isotropic transition curve adopts a zigzag path and the nematic-isotropic transition curve steeply rises and then falls in the phase diagram and behaves in normal manner. An odd–even effect is absent in the nematic-isotropic transition curve with an alteration of transition temperatures. The average thermal stability for the nematic mesophase is 153.1°C, and the nematogenic temperature ranges vary from 12°C to 50°C. Analytical data confirm the molecular structures of the homologues. The Liquid Crystal properties and transition temperatures were observed through an optical polarizing microscope, equipped with a heating stage. The mesomorphic characteristics of the novel ester series are compared with other, known and structurally similar series. The novel series is predominantly nematogenic with the absence of any smectogenic character, with relatively short mesophase temperature ranges and of the middle ordered melting type.

Zigzag modes in quantum cascade laser emission spectra

We present emission spectra obtained from ridge waveguide quantum cascade (QC) lasers with atypical periodic features that result from optical modes that suffer total internal sidewall reflections and traverse zigzag paths along the length of the waveguide structure. These “zigzag” modes are equally spaced, in frequency, about the single lasing mode that arises at threshold. Moreover, they only exist at relatively low injection currents and with increasing current yield to the broadband Fabry–Perot modes that typically comprise the complicated spectra of QC lasers. A straightforward geometric analysis shows a clear correspondence between the zigzag modes and parameters useful for characterizing the quality of the laser waveguide structure.

Design of a New Parametric Path Plan for Additive Manufacturing of Hollow Porous Structures With Functionally Graded Materials

In this paper, a novel path planning approach is proposed to generate porous structures with internal features. The interconnected and continuous deposition path is designed to control the internal material composition in a functionally graded manner. The proposed layer-based algorithmic solutions generate a bilayer pattern of zigzag and spiral toolpath consecutively to construct heterogeneous three-dimensional (3D) objects. The proposed strategy relies on constructing Voronoi diagrams for all bounding curves in each layer to decompose the geometric domain and discretizing the associated Voronoi regions with ruling lines between the boundaries of the associated Voronoi regions. To avoid interference among ruling lines, reorientation and relaxation techniques are introduced to establish matching for continuous zigzag path planning. In addition, arc fitting is used to reduce over-deposition, allowing nonstop deposition at sharp turns. Layer-by-layer deposition progresses through consecutive layers of a ruling-line-based zigzag pattern followed by a spiral path deposition. A biarc fitting technique is employed through isovalues of ruling lines to generate G1 continuity along the spiral deposition path plan. Functionally graded material properties are then mapped based on a parametric distance-based weighting technique. The proposed approach enables elimination or minimization of over-deposition of materials, nonuniformity on printed strands and discontinuities on the toolpath, which are shortcomings of traditional zigzag-based toolpath plan in additive manufacturing (AM). In addition, it provides a practical path for printing functionally graded materials.

Performance of Two Reactors Used to Remove Silica from Water with Electrogenerated Al(OH)3

Two reactors were tested to generate Al3+, that quickly form Al(OH)3 used to remove dissolved silica. Reactor (A) has parallel plates with a vertical zig-zag hydraulic path; this configuration has the disadvantage of important load lost due to the opposition between a going down water flux and the electrochemically generated gas bubbles naturally moving up in some regions. Reactor (B) consisted on an alternating arrangement of a reaction camera with only ascendant flow of water, followed by a chamber designed for water drop. The reaction zone, where bubbles generate is the same where the water moves up. Reactor (B) saves energy and had a better performance for equivalent conditions when compared with reactor (A) to remove silica.

Evaluation of Metallic Mold Surfaces Polished by an Industrial Robot with Stick Whetstones

Our ultimate goal is to develop an automatic polishing system that uses an industrial robot equipped with whetstones. The robot mimics the movements skilled workers make as they polish surfaces manually. This paper, the first step in the development of our system, presents experimental results to prove that our system completely removes the marks, which is the most time-consuming and crucial process for human workers, from the flat surfaces of metallic molds produced through the Electrical Discharge Machining (EDM) process. We build a polishing system that consists of a small 6-DOF industrial robot for material handling. Attached to its wrist is a six-axis force-torque sensor and it employs a whetstone holding mechanism. Before the robot system begins its polishing work, the normal force to be applied to the flat surface can be adjusted to a target value by altering the height of the hand. We adopt two polishing paths for the whetstone, reciprocating and zigzag. We then conduct experiments using the two paths, visually inspect the surface, and measure the surface roughness and shape. Based on the experimental results, we confirm that the system has completely removed the EDM mark layer. Although we find that the zigzag path leaves striped patterns on the polished surface, we are not able to determine their cause. Finally, we test three combinations of the two paths under different conditions to find the most suitable combination.

High-Performance Low-Divergence Angled Laser Diodes With Two-Dimensionally Tilted Sidewalls

High-performance low-divergence angled laser diodes are proposed and fabricated at a wavelength of 910 nm. Light is reflected both inward to the waveguide and downward to the lower cladding layer by the 2-D tilted sidewalls along its zigzag path in the waveguide, and thus the mode field is extended and the transverse divergence angle is greatly reduced. Experimentally, reduced transverse divergence angles by over 20° are demonstrated in both pulse and continuous wave modes, and stable and narrow lateral divergence angles are simultaneously achieved. This device shows a promising future for improving the transverse far-field pattern by surface structure with easy fabrication.

Effect of Corrosion Damage on Fatigue Crack Initiation Mechanism and Growth Behavior of High Strength Aluminum Alloy

Corrosion damage are simulated through accelerated corrosion testing based on the complied environment spectrum, as result of high humidity atmosphere, salt fog, sulfur dioxide, acid rain and dry/wet alternation for aircraft structure during service.Prior corrosion and fatigue experiments are conducted for single edge notched specimen machined from 7B04-T74 advanced high strength aluminum alloy of aircraft critical structure. And the influence of different corrosion damage on fatigue crack initiation and propagation behavior is analyzed, as well as crack growth rate and fatigue life, to find the mechanism of corrosion damage on fatigue behavior. The results indicate that crack initiation site is mainly single pit in early corrosion stage, and the crack follows a relatively straight path. While the corrosion damage grows more severely, multiple small cracks initiate from several pits and there is obvious tunneling effect beneath pits, cracks follow zigzag path. The material microstructures compete with corrosion pits as crack origins.Corrosion damage seriously decreases fatigue life of aluminum alloy. Fatigue crack initiation life with corrosion damage equivalent to 12 years is only 2.2% of that without damage, which indicates crack initiation life is especially sensitive to corrosion damage.

New Aspects of Regions whose Tilings are Enumerated by Perfect Powers

In 2003, Ciucu presented a unified way to enumerate tilings of lattice regions by using a certain Reduction Theorem (J. Algebraic Combin., 2003). In this paper we continue this line of work by investigating new families of lattice regions whose tilings are enumerated by perfect powers or products of several perfect powers. We prove a multi-parameter generalization of Bo-Yin Yang's theorem on fortresses (Ph.D. thesis, MIT, 1991). On the square lattice with zigzag paths, we consider two particular families of regions whose numbers of tilings are always a power of 3 or twice a power of 3. The latter result provides a new proof for a conjecture of Matt Blum first proved by Ciucu. We also consider several new lattices obtained by periodically applying two simple subgraph replacement rules to the square lattice. On some of those lattices, we get new families of regions whose numbers of tilings are given by products of several perfect powers. In addition, we prove a simple product formula for the number of tilings of a certain family of regions on a variant of the triangular lattice.