101 research outputs found
3D Activity Recognition using Motion History and Binary Shape Templates
This paper presents our work on activity recognition in 3D depth images. We propose a global descriptor that is accurate, compact and easy to compute as compared to the state-of-the-art for characterizing depth sequences. Activity enactment video is divided into temporally overlapping blocks. Each block (set of image frames) is used to generate Motion History Templates (MHTs) and Binary Shape Templates (BSTs) over three different views - front, side and top. The three views are obtained by projecting each video frame onto three mutually orthogonal Cartesian planes. MHTs are assembled by stacking the difference of consecutive frame projections in a weighted manner separately for each view. Histograms of oriented gradients are computed and concatenated to represent the motion content. Shape information is obtained through a similar gradient analysis over BSTs. These templates are built by overlaying all the body silhouettes in a block, separately for each view. To effectively trace shape-growth, BSTs are built additively along the blocks. Consequently, the complete ensemble of gradient features carries both 3D shape and motion information to effectively model the dynamics of an articulated body movement. Experimental results on 4 standard depth databases (MSR 3D Hand Gesture, MSR Action, Action-Pairs, and UT-Kinect) prove the efficacy as well as the generality of our compact descriptor. Further, we successfully demonstrate the robustness of our approach to (impulsive) noise and occlusion errors that commonly affect depth data
Recommended from our members
Fabrication of glass sphere laser fusion targets
We have developed processes at LLL for mass producing the high quality glass microspheres required for current laser fusion targets. Here we describe the methods and the materials used in our liquid-droplet and dried-gel systems. Glass microspheres ranging from 70 to 600 microns O.D., with walls from 0.5 to 18 microns thick and which satisfy the exacting surface and symmetry specifications of targets for high density experiments are now produced routinely
A 3D Human Posture Approach for Activity Recognition Based on Depth Camera
Human activity recognition plays an important role in the context of Ambient Assisted Living (AAL), providing useful tools to improve people quality of life. This work presents an activity recognition algorithm based on the extraction of skeleton joints from a depth camera. The system describes an activity using a set of few and basic postures extracted by means of the X-means clustering algorithm. A multi-class Support Vector Machine, trained with the Sequential Minimal Optimization is employed to perform the classification. The system is evaluated on two public datasets for activity recognition which have different skeleton models, the CAD-60 with 15 joints and the TST with 25 joints. The proposed approach achieves precision/recall performances of 99.8 % on CAD-60 and 97.2 %/91.7 % on TST. The results are promising for an applied use in the context of AAL
Magneto‐structural studies of paramagnetic metal cages
A central concern within the field of molecular magnetism has been the elucidation of magneto-structural
correlations. This thesis describes a variety of systems and endeavours to study the
relationship between structure and magnetic properties in these systems. The first body of work
(chapters 2 and 3) studies CrIII dimers, with the metal centres displaying a dialkoxo bridging moiety
and latterly an additional carboxylate bridge to direct the synthesis of ferromagnetic analogues. The
second section of work (chapters 4‐6) moves forward to the study of larger, heterometallic 3d‐3d
compounds, through the synthesis of a large family of Anderson type MIII
2MII
5 wheels and a
subsequent family of (VIVO)2MII
5 wheels.
Chapter 2 describes a series of di‐alkoxo bridged Cr(III) dimers, synthesised using the pyridine alcohol
ligands 2‐pyridinemethanol (hmpH) and 2‐pyridineethanol (hepH) as well as 2‐picolinic acid (picH).
The structures fall into four general categories and are of formula: [Cr2(OMe)2(pic)4],
[Cr2(hmp)2(pic)2X2] (where X = Cl, Br), [Cr2(L)2Cl4(A)2] (where L = hmp, A = H2O; L = hmp, A = pyridine; L
= hmp, A = 4‐picoline; L = hep, A = H2O), and [Cr(hmp)(hmpH)Cl2. Magnetic studies show relatively
weak antiferromagnetic exchange interactions between the Cr(III) centres and DFT calculations are
used to develop magneto‐structural correlations, showing that the magnitude and sign of the J value
is strongly dependent upon the orientation of the dihedral angle formed between the bridging Cr2O2
plane and the O–R vector of the bridging group, and the Cr–O–Cr–O dihedral angle.
Chapter 3 builds on the work from the previous chapter with discussion of a large family of
chromium(III) dimers, synthesised using a combination of carboxylate and diethanolamine type
ligands. The compounds have the general formula [Cr2(R1‐deaH)2(O2CR2)Cl2]Cl where R1 = Me and R2 =
H, Me, CMe3, Ph, 3,5‐(Cl)2Ph, (Me)5Ph, R1 = Et and R2 = H, Ph. The compound [Cr2(Me‐deaH)2Cl4] was
also synthesised in order to study the effect of removing/adding the carboxylate bridge to the
observed magnetic behaviour. Magnetic studies reveal ferromagnetic exchange interactions between
the Cr(III) centres in the carboxylate bridged family with coupling constants in the range +0.37 < J <
+8.02 cm‐1. Removal of the carboxylate to produce the dialkoxide‐bridged compound results in
antiferromagnetic exchange between the Cr(III) ions. DFT calculations to further develop the magneto-structural
correlations reveal the ferromagnetic exchange is the result of an orbital counter-complementarity
effect occurring upon introduction of the bridging carboxylate.
Chapter 4 reports a family of heterometallic Anderson‐type ‘wheels’ of general formula
[MIII
2MII
5(hmp)12](ClO4)4 (where MIII = Cr or Al and MII = Ni or Zn giving [Cr2Ni5], [Cr2Zn5], [Al2Ni5] and
[Al2Zn5]; hmpH = 2‐pyridinemethanol) synthesised solvothermally. The metallic skeleton describes a
centred hexagon with the MIII sites disordered around the outer wheel. The structural disorder is
characterised via single crystal X‐ray crystallography, 1‐3D 1H and 13C solution‐state NMR spectroscopy
of the diamagnetic analogue, and solid‐state 27Al MAS NMR spectroscopy of the Al containing
analogues. Alongside ESI mass spectrometry, these techniques show that structure is retained in
solution, and that the disorder is present in both the solution and solid‐state. Solid‐state dc
susceptibility and magnetisation measurements on [Cr2Zn5] and [Al2Ni5] reveal the Cr‐Cr and Ni‐Ni
exchange interactions to be JCr‐Cr = ‐1 cm‐1 and JNi‐Ni,r = ‐5 cm‐1, JNi‐Ni,c = 10 cm‐1. Fixing these values
allows us to extract JCr‐Ni,r = ‐1.2 cm‐1, JCr‐Ni,c = 2.6 cm‐1, the exchange between adjacent Ni and Cr ions
on the ring is antiferromagnetic and between Cr ions on the ring and the central Ni ion is
ferromagnetic.
Chapter 5 focusses on planar molecules, espanding the family of heterometallic Anderson‐type
‘wheels’ discussed in chapter 4 to include MIII = Cr, Al and MII = Co, Fe, Mn, Cu, affording five new
species of formulae [Cr2Co5(hmp)12](ClO4)4, [Cr2Fe5(hmp)12](ClO4)4, [Cr2Mn5(hmp)12](ClO4)4,
[Cr2Cu5(hmp)12](ClO4)2(NO3)2 and [Al2Co5(hmp)12](ClO4)4. As per previous family members, the two MIII
sites are disordered around the outer wheel, with the exception of [Cr2Cu5] where the the CuII sites
are localised. A structurally related, but enlarged planar disc possessing a [MIII
6MII] hexagon capped
on each edge by a CuII ion is also reported, which is formed only when MIII = Al and MII = Cu. In
[AlIII
6CuII
7(OH)12(hmp)12](ClO4)6(NO3)2 the Anderson moiety contains a central, (symmetry‐imposed)
octahedral CuII ion surrounded by a wheel of AlIII ions. Solid‐state dc susceptibility and magnetisation
measurements reveal the presence of competing exchange interactions in the Anderson wheels
family, and weak antiferromagnetic exchange between the CuII ions in [Al6Cu7].
Chapter 6 describes two heterometallic wheels of formula [(VIVO)2MII
5(hmp)10Cl2](ClO4)2∙2MeOH
(where MII = Ni or Co) displaying the same Anderson‐type structure as seen in chapters 4 and 5,
however the use of the vanadyl moiety has the effect of removing the disorder, with the two vanadyl
ions sitting on opposing sides of the ring. The magnetic properties of both show competing antiferroand
ferromagnetic interactions
Elektrencephalographische Untersuchungen �ber die Wirkung von Weckaminen (Isophen, Pervitin) bei Epileptikern
Zur Frage der Abh�ngigkeit des Sauerstoffverbrauchs vom K�rpergewicht bei Gastropoden und Bivalviern
- …