Chatter avoidance via structural modification of tool-holder geometry

Chatter is a self-excited vibration that can occur during milling operations causing undesirable consequences such as poor surface finish and increased levels of tool wear. One possible solution to this problem is to optimise the dynamics of the machine by tuning parameters such as tool stickout length, e.g. by using receptance coupling substructure analysis. Unfortunately, experimental limitations of the method, such as the requirement to model interface dynamics and the inefficient optimisation process, have hindered its advancement to the industrial sector. This paper looks to resolve these issues by proposing a new structural modification method for chatter avoidance. Firstly, tool-holder diameter is investigated as a potential tuning parameter: a new experimental dataset demonstrates that this design parameter can have a significant and valuable impact on the chatter stability. Secondly, the direct structural modification method is introduced, allowing the tool-holder diameter to be modelled without any knowledge of the interface behaviour between tool and tool-holder. Thirdly, the inverse structural modification method is proposed, allowing tuning and stability optimisation by solving a single equation. Lastly, a new tunable-mass tool-holder is presented, allowing the dynamics of a milling machine to be tuned for each tool diameter and length range with a single tool-holder . This eliminates the need for manufacturers to purchase a wide range of tool-holders, a significant financial investment

Liquid meal composition, postprandial satiety hormones, and perceived appetite and satiety in obese women during acute caloric restriction

OBJECTIVE: The purpose of this study was to compare postprandial satiety regulating hormone responses (pancreatic polypeptide (PP) and peptide tyrosine tyrosine (PYY)) and visual analog scale- (VAS) assessed perceived appetite and satiety between liquid high-protein (HP) and high-carbohydrate (HC) meals in obese women during acute (24-h) caloric restriction. DESIGN: Eleven obese premenopausal women completed two conditions in random order in which they consumed 1500 calories as six 250-calorie HP meals or six 250-calorie HC meals over a 12-h period. Blood samples were taken at baseline and every 20 min thereafter and analyzed for PP and PYY concentrations. At these same points, perceived hunger and fullness were assessed with a VAS. The incremental area under the curve (iAUC) was used to compare postprandial responses. RESULTS: THE 12-H PP AND PYY IAUC WERE GREATER (P0.05) DURING THE HP CONDITION (PP: 4727±1306 pg/ml×12 h, PYY: 1373±357 pg/ml×12 h) compared with the HC condition (PP: 2300±528 pg/ml×12 h, PYY: 754±246 pg/ml×12 h). Perceived hunger and fullness were not different between conditions (P>0.05). The greatest changes in PYY and perceived fullness occurred after the morning meals during both conditions. CONCLUSIONS: These data suggest that in obese women during acute caloric restriction before weight loss, i) liquid HP meals, compared with HC meals, result in greater postprandial PP and PYY concentrations, an effect not associated with differential appetite or satiety responses, and ii) meal-induced changes in PYY and satiety are greatest during the morning period, regardless of dietary macronutrient composition

Control of flexible structures using model predictive control and gaussian processes

There is a recognised need to address issues of vibration control by making use of recent developments in data-driven modelling. The present study considers the difficulties imposed by the limitations of the actuator in the range of active vibration control. The paper proposes and examines a data-based Gaussian process (GP) model of a proof mass actuator in a flexible structural framework, aiming to improve control performance. This requires incorporating an inverse GP of static nonlinearity within the Wiener-Hammerstein model. The model starts with designing model predictive control (MPC) for a cantilever beam, in which the aim is to identify the optimal control force. Utilising the GP is the second step towards quantifying the uncertainty and limitation of the proof mass actuator by designing an inverse GP for the static nonlinearity. This quantification forwards to an MPC controller using a steady-state target optimisation tracking approach, in which this controller provides the optimal voltage required to eliminate vibration within the controller's limitations. The numerical outcome shows that the proposed scheme was capable of supplying the necessary voltage, which eliminated the structure's vibration within an actuator's limits. The results of this work encourage additional research into the developed strategy, particularly in the context of experimental real-time implementation

CX3CR1+ interstitial dendritic cells form a contiguous network throughout the entire kidney

Dendritic cells (DCs) interface innate and adaptive immunity in nonlymphoid organs; however, the exact distribution and types of DC within the kidney are not known. We utilized CX3CR1GFP/+ mice to characterize the anatomy and phenotype of tissue-resident CX3CR1+ DCs within normal kidney. Laser-scanning confocal microscopy revealed an extensive, contiguous network of stellate-shaped CX3CR1+ DCs throughout the interstitial and mesangial spaces of the entire kidney. Intravital microscopy of the superficial cortex showed stationary interstitial CX3CR1+ DCs that continually probe the surrounding tissue environment through dendrite extensions. Flow cytometry of renal CX3CR1+ DCs showed significant coexpression of CD11c and F4/80, high major histocompatibility complex class II and FcR expression, and immature costimulatory but competent phagocytic ability indicative of tissue-resident, immature DCs ready to respond to environment cues. Thus, within the renal parenchyma, there exists little immunological privilege from the surveillance provided by renal CX3CR1+ DCs, a major constituent of the heterogeneous mononuclear phagocyte system populating normal kidney

Rotational degree-of-freedom synthesis: An optimised finite difference method for non-exact data

Measuring the rotational dynamic behaviour of a structure is important for many areas of dynamics such as passive vibration control, acoustics, and model updating. Specialist and dedicated equipment is often needed, unless the rotational degree-of-freedom is synthesised based upon translational data. However, this involves numerically differentiating the translational mode shapes to approximate the rotational modes, for example using a finite difference algorithm. A key challenge with this approach is choosing the measurement spacing between the data points, an issue which has often been overlooked in the published literature. The present contribution will for the first time prove that the use of a finite difference approach can be unstable when using non-exact measured data and a small measurement spacing, for beam-like structures. Then, a generalised analytical error analysis is used to propose an optimised measurement spacing, which balances the numerical error of the finite difference equation with the propagation error from the perturbed data. The approach is demonstrated using both numerical and experimental investigations. It is shown that by obtaining a small number of test measurements it is possible to optimise the measurement accuracy, without any further assumptions on the boundary conditions of the structure

Retinoic acid receptor γ activity in mesenchymal stem cells regulates endochondral bone, angiogenesis, and B lymphopoiesis

Retinoic acid receptor (RAR) signaling regulates bone structure and hematopoiesis through intrinsic and extrinsic mechanisms. This study aimed to establish how early in the osteoblast lineage loss of RARγ (Rarg) disrupts the bone marrow microenvironment. Bone structure was analyzed by micro–computed tomography (μCT) in Rarg–/– mice and mice with Rarg conditional deletion in Osterix‐Cre–targeted osteoblast progenitors or Prrx1‐Cre–targeted mesenchymal stem cells. Rarg–/– tibias exhibited less trabecular and cortical bone and impaired longitudinal and radial growth. The trabecular bone and longitudinal, but not radial, growth defects were recapitulated in Prrx1:RargΔ/Δ mice but not Osx1:RargΔ/Δ mice. Although both male and female Prrx1:RargΔ/Δ mice had low trabecular bone mass, males exhibited increased numbers of trabecular osteoclasts and Prrx1:RargΔ/Δ females had impaired mineral deposition. Both male and female Prrx1:RargΔ/Δ growth plates were narrower than controls and their epiphyses contained hypertrophic chondrocyte islands. Flow cytometry revealed that male Prrx1:RargΔ/Δ bone marrow exhibited elevated pro‐B and pre‐B lymphocyte numbers, accompanied by increased Cxcl12 expression in bone marrow cells. Prrx1:RargΔ/Δ bone marrow also had elevated megakaryocyte‐derived Vegfa expression accompanied by smaller sinusoidal vessels. Thus, RARγ expression by Prrx1‐Cre–targeted cells directly regulates endochondral bone formation and indirectly regulates tibial vascularization. Furthermore, RARγ expression by Prrx1‐Cre–targeted cells extrinsically regulates osteoclastogenesis and B lymphopoiesis in male mice. © 2018 American Society for Bone and Mineral Research

Automorphic Equivalence within Gapped Phases of Quantum Lattice Systems

Gapped ground states of quantum spin systems have been referred to in the physics literature as being `in the same phase' if there exists a family of Hamiltonians H(s), with finite range interactions depending continuously on $s \in [0,1]$, such that for each $s$, H(s) has a non-vanishing gap above its ground state and with the two initial states being the ground states of H(0) and H(1), respectively. In this work, we give precise conditions under which any two gapped ground states of a given quantum spin system that 'belong to the same phase' are automorphically equivalent and show that this equivalence can be implemented as a flow generated by an $s$-dependent interaction which decays faster than any power law (in fact, almost exponentially). The flow is constructed using Hastings' 'quasi-adiabatic evolution' technique, of which we give a proof extended to infinite-dimensional Hilbert spaces. In addition, we derive a general result about the locality properties of the effect of perturbations of the dynamics for quantum systems with a quasi-local structure and prove that the flow, which we call the {\em spectral flow}, connecting the gapped ground states in the same phase, satisfies a Lieb-Robinson bound. As a result, we obtain that, in the thermodynamic limit, the spectral flow converges to a co-cycle of automorphisms of the algebra of quasi-local observables of the infinite spin system. This proves that the ground state phase structure is preserved along the curve of models $H(s), 0\leq s\leq 1$.Comment: Updated acknowledgments and new email address of S

Understanding the Chemical Complexity in Circumstellar Envelopes of C-rich AGB Stars: the Case of IRC +10216

The circumstellar envelopes of carbon-rich AGB stars show a chemical complexity that is exemplified by the prototypical object IRC +10216, in which about 60 different molecules have been detected to date. Most of these species are carbon chains of the type CnH, CnH2, CnN, HCnN. We present the detection of new species (CH2CHCN, CH2CN, H2CS, CH3CCH and C3O) achieved thanks to the systematic observation of the full 3 mm window with the IRAM 30m telescope plus some ARO 12m observations. All these species, known to exist in the interstellar medium, are detected for the first time in a circumstellar envelope around an AGB star. These five molecules are most likely formed in the outer expanding envelope rather than in the stellar photosphere. A pure gas phase chemical model of the circumstellar envelope is reasonably successful in explaining the derived abundances, and additionally allows to elucidate the chemical formation routes and to predict the spatial distribution of the detected species.Comment: 4 pages, 4 figures; to appear in Astrophysics and Space Science, special issue of "Science with ALMA: a new era for Astrophysics" conference, November, 13-17 2006, ed. R. Bachille