Digital Shape Research Articles

Characterization of shape diversity in bat biosonar beampatterns

Numerical beampattern estimates for a large digital shape data set with 361 three-dimensional models of the pinna and noseleaf shapes from 106 different bat species are currently in preparation. Shape samples in this data set have been selected to represent taxonomic diversity and balance noseleaves versus pinnae. The data set will be used to analyze the biodiversity in bat beampatterns. In order to facilitate the extraction of interspecific patterns, spherical harmonics are being evaluated as an analysis tool to describe the spatial frequency content of the beampatterns. Spherical harmonics are the angular portion of a set of solutions to Laplace's equation represented in a system of spherical coordinates. The higher the harmonic, the more solutions are in the respective set. Regardless of the number of solutions, each set forms an orthogonal system. For a compressed characterization of the beampatterns, the representation of the beampattern shape at a given frequency is expressed as a power spectrum; the norm of the vector of the weighting coefficients for all basis functions in the set of a harmonic is taken to represent the portion of the total power explained by a particular harmonic. This power spectrum was found to reflect several beampattern properties well.

Ascending in Space Dimensions: Digital Crafting of M.C. Escher's Graphic Art

M.C. Escher's artwork has inspired and arguably even informed computer science, as well as geometric and shape modeling. Even today, much of his work poses challenges to conventional digital shape modeling systems. The authors introduce several interesting problems presented by Escher's graphic artworks and describe their use of a novel approach, based on implicit surfaces and their extension (Function Representation), to produce 2D, 2.5D and 3D computer models. They also discuss several physical objects or sculptures based on these models, crafted using digital fabrication processes.

On gamma-ray spectrometry pulses real time digital shaping and processing

In gamma-ray medical imaging and nuclear spectroscopy instruments, deployment of high speed reconfigurable field programmable gate arrays circuits make it possible to implement signal processing algorithms for pulse shaping, pile up detection and correction, and determination of pulse amplitude and its time of detection in real time. Based on this idea, we have developed a digital pulse processing board for use in a gamma ray spectroscopy and later in positron emission tomography. The proposed digital pulse-processing core relies on digital trapezoidal or triangular pulse shaping, an automatic baseline correction and pileup rejection methods, all of which are implemented in FPGA to permit on-line event processing. Experimental results show that because of its pulse shaping method, system throughput and energy resolution significantly outperforms analog pulse processing systems.

Study of Pulse Shape Discrimination of Sub-MeV Neutrons From Gamma-Rays with Liquid Scintillator

We have studied pulse shape discrimination of sub-MeV neutron from spallation nuclear reactions. Neutron measurements were carried out with a 2-inch NE213 scintillator viewed by a phototube (HAMAMATSU H1949) for the carbon-carbon reaction at 290 MeV/n. Neuron energies were measured with the TOF technique by using a timing pick-up plastic scintillator. Output signals of detectors were digitized and stored with a digitizer (Acqiris DC282). The digital pulse shape discrimination (DPSD) has been investigated through comparison between three different analyzing algorithms. Effects on the neutron-gamma (n/g) discrimination were also investigated after the subtraction of background and abnormal events. Moreover, in order to realize better n/g discrimination the detector system was cooled down to about zero degrees centigrade by Peltier devices to suppress the dark current of the phototube which would be the main cause distorting pulse shapes. Experimental studies were made in terms of the temperature dependence of detector performance including pulse shape.

Normal Location Of Thumb/Big Toe may be Related to Programmed Cell Death in the Preaxial Area of Embryonic Limb

The forelimbs and hindlimbs of newborn Polydactyly Nagoya (Pdn) mice were examined to analyze the roles of programmed cell death (PCD) in the preaxial region of the limb. Special attention was paid to the relationship between the PCD in the preaxial area and the location and shape of the first digit (thumb/big toe). Although a large, bifurcated or duplicated thumb/big toe appeared in Pdn/+ mice, digit I (thumb/big toe) in Pdn/+ mice, as in +/+ ones, was located more ventro-proximally than the other four digits. On the other hand, abnormal preaxial digits of the fore/hindlimb in Pdn/Pdn mice lay distally and were aligned at the radial/tibial end of a serial curved plane formed by digits II-V; that is, a thumb and big toe of normal shape and location were not detectable in any preaxial digits of Pdn/Pdn mice. In the limb development of Pdn mouse embryos on Day 11-12, PCD did not occur in the preaxial mesoderm of fore/hindlimb only in one-fourths of all embryos obtained by Pdn/+ x Pdn/+ mating. In addition to digital rays II-V, extra preaxial digital rays appeared in the prominent preaxial expansion of fore/hindlimbs in these embryos on early Day 12. These abnormal limb configurations in embryos were closely similar to those in Pdn/Pdn newborn mice. The present findings suggest that PCD in the preaxial region not only prevents the formation of extra digits but also determines the location of the thumb/big toe for the normal limb morphogenesis.

Bidirectional Shaping and Spaces of Convergence

This article proposes a new bi-directional way of understanding the convergence of biology and computing. It argues for a reciprocal interaction in which biology and computing have shaped and are currently reshaping each other. In so doing, we qualify both the view of a natural marriage and of a digital shaping of biology, which are common in the literature written by scientists, STS, and communication scholars. The DNA database is at the center of this interaction. We argue that DNA databases are spaces of convergence for computing and biology that change in form, meaning, and function from the 1960s to the 2000s. The first part of the article shows how, in the 1980s, DNA sequencing shifted from passively incorporating computers to be increasingly modeled in digital coding and decoding. Information retrieval algorithms, reciprocally, were altered according to the peculiarities of DNA in the first sequence-storage databases. The second part of the article investigates the impact of these reciprocal interactions and globalization on the organization of research centers, ways of conducting big science, and scientific values. Through convergence and new technologies such as data mining, biology and computing were transformed technologically, institutionally, and culturally into a new bio-data enterprise called genomics.

A Digital Near Net Shape Manufacturing Propeller with Complex Surface

An integrated digital routine is applied in the near net shape manufacturing of marine propeller. Firstly, the 3D CAD file of propeller is created by parametric modeling. Secondly, the propeller casting process is simulated using CAE software, through which an optimized casting scheme is obtained. Thirdly, fabricates the mold using laser rapid prototyping and cast the metal propeller. Finally, evaluate the casting precision performance. CAD, CAE and CAM are integrated in this process. The dimensional accuracy of the final piece is controlled within 1mm and its surface roughness achieves Ra 6.3μm. The result shows that the pattern-less casting of propeller can be achieved by this method, reducing cost and performing high accuracy.

Investigation of high energy γ-rays accompanying spontaneous fission of 252Cf in double and triple neutron-γ coincidences

The high energy bremsstrahlung γ-rays accompanying the spontaneous fission of 252 Cf were measured in the 10–70 MeV energy range. The photons were detected by two BGO scintillator detectors (ø7.6cm × 7.6cm) in coincidence with neutrons detected by plastic scintillator detector, in the 90° and 180° geometry of the two BGO detectors with respect to the axis of the plastic scintillator. The distance from the 252Cf source to the BGO detectors was 10 cm, and the one to the plastic detector was 50 cm. The fast digital shape analysis technique and the time-of-flight method were used to reject pile-up effects and cosmic ray background. The γ-ray emission probability of 3 × 10−8photon/(MeV × fission) at Eγ = 70 MeV was obtained.

Digital Pulse Width Modulation For Half Bridge Amplifiers

A switching amplifier drives a load or audio transducer. A digital integral noise shaping circuit converts a digital input such as audio content to an output digital pulse width modulated signal using an integrator. The integrator integrates the digital input, a variable frequency reference pulse width modulated signal and an inverse of the output digital pulse width modulated signal. A half bridge amplifier receives the output digital pulse width modulated signal and drives the load or audio transducer. A variable frequency generator generates the variable frequency reference pulse width modulated signal with an approximately equal duty ratio or alternatively varies the variable frequency pulse width modulated signal above and below about a fifty percent duty ratio.

KNOWLEDGE-BASED REPRESENTATION OF 3D MEDIA

In recent years, 3D media have become more and more widespread and have been made available in numerous online repositories. A systematic and formal approach for representing and organizing shape-related information is needed to share 3D media, to communicate the knowledge associated to shape modeling processes and to facilitate its reuse in useful cross-domain usage scenarios. In this paper we present an initial attempt to formalize an ontology for digital shapes, called the Common Shape Ontology (CSO). We discuss about the rationale, the requirements and the scope of this ontology, we present in detail its structure and describe the most relevant choices related to its development. Finally, we show how the CSO conceptualization is used in domain-specific application scenarios.

A CAD system based on haptic modelling for conceptual design

The paper presents the results of a research project aiming to develop an innovative framework for the conceptual design of products based on haptic technology. The system consists of a Computer-Aided Design (CAD) system enhanced with intuitive designer-oriented interaction tools and modalities. The system integrates innovative haptic tools with 6 Degrees of Freedom (DOF) for modelling digital shapes, with sweep operators applied to class-A surfaces and force computation models based on chip formation models. The system aims to exploit designers' skills in modelling products, improving the products' design process by reducing the necessity to build several physical models for the evaluation and testing of product designs. The system requirements have been defined after observing designers during their daily work and translating the way they model shapes using their hands and craft tools into specifications for the system. The system has been tested by designers, who have found it intuitive and effective to use.

An Input Shaping Filter

The method of control signal shaping has been practically used in control systems with flexible elements since the end of 80th years of last century. The most of applications has been focused on machine engineering, e. g. speedy elevators, cranes, etc. New techniques for design of train of impulses improving system robustness appeared in the theory (mainly in time domain). The article presents alternative approach based on discrete shaping filter design as a correction filter with impulse response identical to classical solution (for properly selected filter parameters). Referring to realization of control signal shaping system by digital devices, this approach is more convenient one. The proposed modification, increasing of sampling frequency at the input of digital shaping filter, allows fast system response to control signal changes.

Sculpturing digit shape by cell death

Physiological cell death is a key mechanism that ensures appropriate development and maintenance of tissues and organs in multicellular organisms. Most structures in the vertebrate embryo exhibit defined areas of cell death at precise stages of development. In this regard the areas of interdigital cell death during limb development provide a paradigmatic model of massive cell death with an evident morphogenetic role in digit morphogenesis. Physiological cell death has been proposed to occur by apoptosis, cellular phenomena genetically controlled to orchestrate cell suicide following two main pathways, cytochrome C liberation from the mitochondria or activation of death receptors. Such pathways converge in the activation of cysteine proteases known as caspases, which execute the cell death program, leading to typical morphologic changes within the cell, termed apoptosis. According to these findings it would be expected that caspases loss of function experiments could cause inhibition of interdigital cell death promoting syndactyly phenotypes. A syndactyly phenotype is characterized by absence of digit freeing during development that, when caused by absence of interdigital cell death, is accompanied by the persistence of an interdigital membrane. However this situation has not been reported in any of the KO mice or chicken loss of function experiments ever performed. Moreover histological analysis of dying cells within the interdigit reveals the synchronic occurrence of different types of cell death. All these findings are indicative of caspase alternative and/or complementary mechanisms responsible for physiological interdigital cell death. Characterization of alternative cell death pathways is required to explain vertebrate morphogenesis. Today there is great interest in cell death via autophagy, which could substitute or act synergistically to the apoptotic pathway. Here we discuss what is known about physiological cell death in the developing interdigital tissue of vertebrate embryos, paying special attention to the avian species.

Discriminating contact in lumen with a moving flexible digit using fibre Bragg grating sensing elements

Minimal access procedures in surgery offer benefits of reduced patient recovery time and less pain, yet for the surgeon the task is more complex, as both tactile and visual perception of the working site is reduced. In this paper, experimental evidence of the performance of a novel sensing system embedded in an actuated flexible digit element is presented. The digit represents a steerable tip element of devices such as endoscopes and laparoscopes. This solution is able to discriminate types of contact and tissue interaction, and to feed back this information with the shape of the flexible digit. As an alternative to this information, force level, force distribution, and other quantifiable descriptors can also be evaluated. These can be used to aid perception in processes such as navigation and investigation of tissues through palpation. The solution is pragmatic, and by virtue of its efficient mechanical construction and a polymer construction, it offers opportunities for a disposable element with suitability for magnetic resonance imaging (MRI) and other scanning environments. By using only four photonics sensing elements, full perception of tissue contact and the shape of the actuated digit can be described in the feedback of this information. The distributive sensory method applied to the sensory signals relies on the coupled values of the sensory data transients of the four deployed sensing elements to discriminate tissue interaction directly in near real time.

InterviewAn interview with Ping Fu

Ping Fu, CEO of the digital shape sampling and processing company Geomagic, discusses her background, achievements, and challenges managing a company during a period of dynamic growth.

On-Beam Digital Pulse Shape Acquisition From NE102A-${\rm BaF}_{2}$ Phoswich Detector

The use of NE102A-BaF2 phoswich detector drastically improves the particle identification with respect to BaF2 crystals. To better exploit the possibility of light ion discrimination we have applied digital signal processing to the signals, on-beam collected with NE102A-BaF2 phoswich. We present the results obtained for the heavy ion charge identification (up to Z=50) and light particle mass identification, using digital pulse shape acquisition and a 12-bit, 2 GSample/s sampling analog to digital converter. The results concerning the response of BaF2-plastic phoswich to the reaction products issued at forward angles in the collision of 35.1 MeV/u 124Sn beam on 64Ni target have been obtained at the Superconducting Cyclotron of the Laboratori Nazionali del Sud in Catania.

Processes to Integrate Design With Downstream Applications Through Product Shapes Adaptation

In the aeronautics industry, various stages of a product development process such as physical phenomena (like stress, strain, and thermal ones) or virtual reality simulations are regarded as product views and based on different digital shapes of the same physical component. The shape adaptation processes needed to progress from one stage of the product development process to another one, the multiple shapes needed for a simulation at a given stage of this process are analyzed and shape adaptation operators are presented. Then, it is shown why geometric models adaptation processes from the design stage to downstream applications are important in an industrial design context, and why this is a concurrent engineering enabler. Subsequently, we show how shapes adaptation processes can be achieved through their appropriate formalization and representation using direct acyclic graphs connected to the scene structure of a simulation and the product structure used as input. A process data structure is also proposed to describe shape adaptation processes and ease their reuse. Finally, based on two EADS case studies, we illustrate how methods and criteria can be set up to produce adapted shapes from computer-aided design data in a controlled and integrated manner.

Effect of signal noise on the learning capability of an artificial neural network

Digital Pulse Shape Analysis (DPSA) by artificial neural networks (ANN) is becoming an important tool to extract relevant information from digitized signals in different areas. In this paper, we present a systematic evidence of how the concomitant noise that distorts the signals or patterns to be identified by an ANN set limits to its learning capability. Also, we present evidence that explains overtraining as a competition between the relevant pattern features, on the one side, against the signal noise, on the other side, as the main cause defining the shape of the error surface in weight space and, consequently, determining the steepest descent path that controls the ANN adaptation process.

Content-based similarity for 3D model retrieval and classification

With the rapid development of 3D digital shape information, content-based 3D model retrieval and classification has become an important research area. This paper presents a novel 3D model retrieval and classification algorithm. For feature representation, a method combining a distance histogram and moment invariants is proposed to improve the retrieval performance. The major advantage of using a distance histogram is its invariance to the transforms of scaling, translation and rotation. Based on the premise that two similar objects should have high mutual information, the querying of 3D data should convey a great deal of information on the shape of the two objects, and so we propose a mutual information distance measurement to perform the similarity comparison of 3D objects. The proposed algorithm is tested with a 3D model retrieval and classification prototype, and the experimental evaluation demonstrates satisfactory retrieval results and classification accuracy.

The engineering of patient-specific, anatomically shaped, digits

It is now recognized that geometric structures of scaffolds at several size levels have profound influences on cell adhesion, viability, proliferation and differentiation. This study aims to develop an integrated process to fabricate scaffolds with controllable geometric structures at nano-, micro- and macro-scales. A phase-separation method is used to prepare interconnected poly( l-lactide) (PLLA) nanofibrous (NF) scaffolds. The pore size of the NF scaffold at the scale of several hundred micrometers is controlled by the size of porogen, paraffin spheres. At millimeter scale and above, the overall shape of the scaffold is defined by a wax mold produced using a three-dimensional printer. The printer utilizes a stereo lithographic file generated from computed tomographic files retrieved from the National Library of Medicine's Visual Human Project. NF PLLA scaffolds with a human digit shape are successfully prepared using this process. Osteoblast cell line MC3T3-E1 cells are then seeded and cultured in the prepared scaffolds. Cell proliferation, differentiation and biomineralization are characterized to demonstrate the suitability of the scaffolds for the digit bone tissue engineering application.