Two-part Problem Research Articles

A Covert Jamming Scheme Against an Intelligent Eavesdropper in Cooperative Cognitive Radio Networks

In this work, we design a covert jamming scheme against an intelligent Eve towards physical layer security in a cooperative cognitive radio networks. To protect the primary message from being decoded by an intelligent eavesdropper (Eve), a secondary user is picked as a friendly jammer that transmits artificial noise (AN) to the Eve. However, the intelligent Eve can detect the existence of AN, and thus the AN is inclined to be covertly transmitted at a lower detection probability, thereby mistaking the AN as background noise by the Eve. In this paper, firstly, by using a binary hypothesis testing, the detection error probability (DEP) is explicitly derived for detection performance analysis of the Eve in the perfect as well as statistical channel state information (CSI) scenario, separately. With the DEP, a covert jamming scheme is formulated to transmit the AN in both cases. Then, an optimization problem is formulated, and then recast into a two-part problem to maximize the secrecy performance with the covert jamming scheme in the perfect CSI case. Finally, the effective secrecy throughput is maximized under convert constraints in the statistical CSI case. Numerical results are provided to validate the DEP at the Eve and secrecy performance analysis.

Virtual alignment of pathology image series for multi-gigapixel whole slide images

Interest in spatial omics is on the rise, but generation of highly multiplexed images remains challenging, due to cost, expertise, methodical constraints, and access to technology. An alternative approach is to register collections of whole slide images (WSI), generating spatially aligned datasets. WSI registration is a two-part problem, the first being the alignment itself and the second the application of transformations to huge multi-gigapixel images. To address both challenges, we developed Virtual Alignment of pathoLogy Image Series (VALIS), software which enables generation of highly multiplexed images by aligning any number of brightfield and/or immunofluorescent WSI, the results of which can be saved in the ome.tiff format. Benchmarking using publicly available datasets indicates VALIS provides state-of-the-art accuracy in WSI registration and 3D reconstruction. Leveraging existing open-source software tools, VALIS is written in Python, providing a free, fast, scalable, robust, and easy-to-use pipeline for registering multi-gigapixel WSI, facilitating downstream spatial analyses.

Wrinkling of a compressible trilayer domain under large plane deformations

Instabilities that arise in layered systems have been a riveting course of study for the past few decades, having found utility in various fields, while also being frequently observed in biological systems. The trilayer structure, composed of a film, interphase and substrate, is employed in several applications where the structure undergoes large deformations and the materials used are far from incompressible. Due to their complex behavior and their potential applications, the instabilities of compressible tri-layered systems; as in how they are initiated and how they can be tuned, yet remain elusive and poorly understood. Hence, the main goal of this contribution is to shed light on the large deformation wrinkling behavior of a compressible, trilayer domain, wherein a theoretical solution which captures the instability behavior of a compressible trilayer system under plane deformations is developed. An excellent agreement is observed between the analytical solutions and numerical findings, obtained using FEM enhanced with eigenvalue analysis, for a wide range of geometrical and material parameters, including compressibility of the domains, stiffness ratios, and interphase thickness. The effect of compressibility is found to be particularly significant for the case of a more compliant interphase compared to the substrate. We rigorously establish a theoretical framework that yields a one-part solution for critical wavelength, which alone captures the different wrinkling modes that have been reported in trilayer structures but previously have been treated as a two-part problem. Finally, at the incompressibility limit, the solution here reduces to its counterparts established in literature.

No Single Path: Review of Amy Sullivan's Opioid Reckoning

No Single Path:Review of Amy Sullivan's Opioid Reckoning Jaeyoon Park (bio) Amy Sullivan. Opioid Reckoning: Love, Loss, and Redemption in the Rehab State. Minneapolis: University of Minnesota Press, 2021. 266 pp. $25.95 (hc). ISBN: 9781517908638. "Science can find a cure for our diseases, but not for our societal ills," one reads in a recent opinion column on the pandemic featured in the New York Times.1 Here we have, in aphoristic form, a now-familiar framework that reconciles the brilliant technological success of medical science in the last year with the relentlessness, still, of the COVID-19 pandemic. According to this framework, the pandemic is a two-part problem: one part virus, one part social resistance to the cure for the disease. The framing itself does not show us how to quell the resistance, and yet it charts the path forward. What we need to do in order to halt the pandemic is make the world more ready to be healed by science; what we need is a campaign against public skepticism about the health care system, against scientific illiteracy, and against vicious misinformation about the relative risks of COVID-19 and mRNA injections. This same framework has been circulating for years as an explanation for another health crisis also far from an end in this country: the epidemic of opioid addiction and overdose. In relation to that crisis, too, we hear that science has done its work, but there is resistance to the outcomes of science––hence, the crisis rages on. More precisely, we hear that medical scientists have developed "gold standard" treatments for addiction, but that for reasons of bureaucratic lethargy, public skepticism, or sheer hopelessness among those suffering from addiction, the treatments are not adequately made available and sought out. (The name for this problem, in media and state discourse, is "the treatment gap.") Again, we have the two-part, divided-labor frame: the opioid crisis is part biological illness, part social resistance, and the solution is, first, to develop the technical means to tame the disease; and second, to distribute that technical means among the affected public. Whether or not this framework is adequate for making sense of the COVID-19 pandemic, it certainly fails to capture the realities of the opioid crisis. Of course, the treatment gap is a problem, and the various forms of misunderstanding, ignorance, and misanthropy that render addiction treatment [End Page 225] unavailable for those who want and need it must be defeated. But we mislead ourselves when we think that science has solved the disease problem, and that an end to the crisis will come if we can just disseminate the science, and close down the gap between what medicine already offers and what patients clearly need. For addiction is, in essential respects, not like COVID-19. And there is likely no technical solution for the opioid crisis, here now or waiting in the wings. I cannot, of course, make a full argument for these claims in the space of a book review. But I can show how they are powerfully suggested by what goes on in the actually existing world of opioid addiction treatment, which we may glimpse through the recent work of the historian Amy Sullivan. Amy Sullivan's Opioid Reckoning centers on an often-overlooked set of experiences relating to opioid addiction treatment. We know from the ethnographic work of medical anthropologists such as Philippe Bourgois, Angela Garcia, and Helena Hansen something of the first-person experience of undergoing addiction treatment. And we know, from the many profiles of individuals suffering from opioid addiction featured in newspapers and magazines, something of the life stories into which treatment regimens fit, and of the complex personal circumstances into which treatments aim to intervene. Less often do we learn about the lives and experiences of those who are witness to an addiction and its treatment—as parents, physicians, activists, and community leaders. What is the kind of grief felt by parents who, long prior to the actual death of a child with a severe addiction, sense that the possibility of a long and open future for the child has perhaps already been lost, is unlikely to be...

Rotational Diversity in Multi-Cycle Assignment Problems

In multi-cycle assignment problems with rotational diversity, a set of tasks has to be repeatedly assigned to a set of agents. Over multiple cycles, the goal is to achieve a high diversity of assignments from tasks to agents. At the same time, the assignments’ profit has to be maximized in each cycle. Due to changing availability of tasks and agents, planning ahead is infeasible and each cycle is an independent assignment problem but influenced by previous choices. We approach the multi-cycle assignment problem as a two-part problem: Profit maximization and rotation are combined into one objective value, and then solved as a General Assignment Problem. Rotational diversity is maintained with a single execution of the costly assignment model. Our simple, yet effective method is applicable to different domains and applications. Experiments show the applicability on a multi-cycle variant of the multiple knapsack problem and a real-world case study on the test case selection and assignment problem, an example from the software engineering domain, where test cases have to be distributed over compatible test machines.

This AI hunts poachers

Every year, poachers kill about 27,000 African elephants-an astounding 8 percent of the population. If current trends continue, these magnificent animals could be gone within a decade. The solution, of course, is to stop poachers before they strike, but how to do that has long confounded authorities. In protected areas like wildlife preserves, elephants and other endangered animals may roam far and wide, while rangers can patrol only a small area at any time. It's a two-part problem, explains Milind Tambe, a computer scientist at the University of Southern California, in Los Angeles. Can you predict where poaching will happen? And can you [target] your patrols so that they're unpredictable, so that the poachers don't know the rangers are coming?

Efficient compensation of dimensional errors in robotic machining using imperfect point cloud part inspection data

“Process-to-part” robotic machining using low-cost, off-the-shelf industrial robots is of interest for feature machining applications on large components where mounting on conventional machine tools is costly and presents a health and safety risk. For a range of well documented reasons, low-cost industrial robot-based machine tools are limited in terms of machining tolerance range. Work conducted by the authors in Barnfather et al. (2016a, 2016b, 2016c, 2017a, 2017b) investigates these capabilities as well as on-line dimensional error measurement and compensation using optical scanning methods, which have development potential for low cost dense error measurement. A key problem when optically scanning machined surfaces for error measurement is noise and localised data gaps due to reflectance. Robotic machining error compensation in this way can therefore be thought of as a two-part problem involving acquiring quality scan data and processing it optimally to compensate a machining trajectory. This paper contributes to the latter by presenting a dimensional deviation evaluation method for efficiently computing compensated robotic machining trajectories from aligned optically scanned point clouds without processing redundant data, as is typical in related works. Results validate this method, showing a ∼96% improvement on dimensional error measurement time in comparison to conventional methods, and conclusions are drawn on direction for further development. This method is a novel contribution to the current state of the art of point cloud processing for on-line robotic machining error measurement and compensation, allowing the best to be made of imperfect point cloud inspection scans.

Novel approximate UTD ray solution for the radiation and scattering by antennas near a planar material junction on PEC ground plane

A novel approximate uniform geometrical theory of diffraction (UTD) for analyzing an electromagnetic wave diffracted by a planar material junction on PEC ground plane has been developed in this research. The proposed UTD solution is based on an ansatz obtained from the Weiner–Hopf (W–H) solution by approximating the W–H split functions. This makes the proposed UTD solution to be a relatively simple and closed form expression. Additionally, the proposed UTD solution can deal with both a planar material junction on PEC ground plane and a two-part problem with any types of wave illumination such as a plane wave, a cylindrical wave, and a spherical wave. The accuracy of the proposed UTD solution is compared with the W–H solution and finite different time domain (FDTD) which provides very good agreement. The proposed UTD solution has very small numerical errors. However, the accuracy of the proposed UTD solution is good enough for engineering applications.

Faster, more accurate, parallelized inversion for shape optimization in electroheat problems on a graphics processing unit (GPU) with the real-coded genetic algorithm

Purpose – Inverting electroheat problems involves synthesizing the electromagnetic arrangement of coils and geometries to realize a desired heat distribution. To this end two finite element problems need to be solved, first for the magnetic fields and the joule heat that the associated eddy currents generate and then, based on these heat sources, the second problem for heat distribution. This two-part problem needs to be iterated on to obtain the desired thermal distribution by optimization. Being a time consuming process, the purpose of this paper is to parallelize the process using the graphics processing unit (GPU) and the real-coded genetic algorithm, each for both speed and accuracy. Design/methodology/approach – This coupled problem represents a heavy computational load with long wait-times for results. The GPU has recently been demonstrated to enhance the efficiency and accuracy of the finite element computations and cut down solution times. It has also been used to speedup the naturally parallel genetic algorithm. The authors use the GPU to perform coupled electroheat finite element optimization by the genetic algorithm to achieve computational efficiencies far better than those reported for a single finite element problem. In the genetic algorithm, coding objective functions in real numbers rather than binary arithmetic gives added speed and accuracy. Findings – The feasibility of the method proposed to reduce computational time and increase accuracy is established through the simple problem of shaping a current carrying conductor so as to yield a constant temperature along a line. The authors obtained a speedup (CPU time to GPU time ratio) saturating to about 28 at a population size of 500 because of increasing communications between threads. But this far better than what is possible on a workstation. Research limitations/implications – By using the intrinsically parallel genetic algorithm on a GPU, large complex coupled problems may be solved very quickly. The method demonstrated here without accounting for radiation and convection, may be trivially extended to more completely modeled electroheat systems. Since the primary purpose here is to establish methodology and feasibility, the thermal problem is simplified by neglecting convection and radiation. While that introduces some error, the computational procedure is still validated. Practical implications – The methodology established has direct applications in electrical machine design, metallurgical mixing processes, and hyperthermia treatment in oncology. In these three practical application areas, the authors need to compute the exciting coil (or antenna) arrangement (current magnitude and phase) and device geometry that would accomplish a desired heat distribution to achieve mixing, reduce machine heat or burn cancerous tissue. This process presented does it more accurately and speedily. Social implications – Particularly the above-mentioned application in oncology will alleviate human suffering through use in hyperthermia treatment planning in cancer treatment. The method presented provides scope for new commercial software development and employment. Originality/value – Previous finite element shape optimization of coupled electroheat problems by this group used gradient methods whose difficulties are explained. Others have used analytical and circuit models in place of finite elements. This paper applies the massive parallelization possible with GPUs to the inherently parallel genetic algorithm, and extends it from single field system problems to coupled problems, and thereby realizes practicable solution times for such a computationally complex problem. Further, by using GPU computations rather than CPU, accuracy is enhanced. And then by using real number rather than binary coding for object functions, further accuracy and speed gains are realized.

Thin-film superconducting rings in the critical state: the mixed boundary value approach

In this paper, we describe the critical state of a thin superconducting ring (and of a perfectly conducting ring as a limiting case) as a mixed boundary value problem. The disc is characterized by a three-part boundary division of the positive real axis, so this work is an extension of the procedure used in a previous work of ours for describing superconducting discs and strips, which are characterized by a two-part boundary division of the real axis. Here, we present the mathematical tools to solve this kind of problems—the Erdelyi–Kober operators—in a frame that can be immediately used. Contrary to the two-part problems considered in our previous work, three-part problems do not generally have analytical solutions and the numerical work takes on a significant heaviness. Nevertheless, this work is remunerated by three clear advantages: firstly, all the cases are afforded in the same way, without the necessity of any brilliant invention or ability; secondly, in the case of superconducting rings, the penetration of the magnetic field in the internal/external rims is a result of the method itself and does not have to be imposed, as it is commonly done with other methods presented in the literature; thirdly, the method can be extended to investigate even more complex cases (four-part problems). In this paper, we consider the cases of rings in uniform field and with transport current, with or without flux trapping in the hole and the case without net current, corresponding to a cut ring (washer), as used in some SQUID applications.

Sensing Service Delivery: Pervasive Computing and Governance in Developing Countries

Despite having transitioned to democracy, the governments of many developing countries still deliver poor public services as measured by social outcome indicators. Recent literature frames these issues of governance and public service delivery as a two-part principal-agent problem: civil servants are the agents of politicians and politicians are themselves the agents of the voters (Olken and Pande 2011). Much of this literature explores the determinants that drive citizens to demand better services (Pande 2011). Less attention, however, has been paid to understanding the behavior of the agents themselves and the interventions that can lead local politicians and civil servants to deliver better services.

A General Iterative Procedure of the Non-Numerical Ranking Preferences Method for Multiple Objective Decision Making

Multiple objective evolutionary algorithms (MOEAs), which are biologically-inspired optimization methods, have become popular approaches to solve problems with multiple objective functions. With the use of MOEAs, multiple objective optimization becomes a two-part problem. First, the multiple objective optimization problem needs to be formulated and successfully solved using an MOEA. Then, a non- dominated set -also known as efficient or Pareto frontier- needs to be analyzed to select a solution to the problem. This can represent a challenging task to the decision-maker because this set can contain a large number of solutions. This decision- making stage is usually known as the post-Pareto analysis stage. This paper presents the generalization of a post-Pareto optimality method known as the non-numerical ranking preferences (NNRP) method originally proposed by Taboada et al. (2007). This method can help decision makers reduce the number of design possibilities to small subsets that clearly reflect their objective function preferences. Previous research has only presented the application of the NNRP method using three and four objective functions but had not been generalized to the case of n objective functions. The present paper expands the NNRP method to be able to consider multiple objective optimization problems with n number of objective functions.

How Many Workers Have to Die for Apparel Brands to Change their Game?

FOCUS O BUSINESS ANDHUMANRIGHTS How Many Workers Have to Die for Apparel Brands to Change their Game? I programmes improve conditions failed have meaningful monitoring Corporate to working change tried deliver have that to monitoring programmesthat have triedto improveworking conditionshave failedto deliver meaningful change JUDY GEARHART is Executive Director off the International Labor Rights Forum in Washington On nessed ever 11September inthe two history of and the of 24 worst the November, apparel industrial industry: we fires witnessed two of the worstindustrial fires everinthehistory oftheapparelindustry: 262 workers died at Ali Enterprises in Pakistan and 112werelosttothefire atTazreenFashions inBangladesh. Since2006,morethan6OOworkers have died in majorfactory catastrophes in Bangladesh making clothesforexport. Workers who survive factory fires report exits were blockedby product, or even locked,fire escapeswerenon-existent, barred windowsprevented alternateescapes and panic overtook everyone. Whenworkershave raisedconcerns they've often been sentback to their stations or dismissed. Itistimeformultinational apparelcorporations tojoinan industry-wide initiative that is transparent ,binding, and committed to including local workers inensuring workplace safety. Formorethantwodecadesapparelcompanies have been steadily movingproduction offshore, divorcing themselves from production and focusingon design,marketing and logistics. Thishas resulted ingaping flaws inthewayourclothes are made. Corporatemonitoring programmes that havetried toimprove working conditions inexport processing abroadhavefailed todeliver meaningful change,as the recenthorrific tragediesin Pakistan andBangladesh so painfully remind us. Companieshave arguedthatordering apparel from poorcountries is good foreconomicdevelopment ingeneral anda blessing towomenworkersinparticular . Infact, as economic development goes,investing inwomen'slivelihoods is generallya goodthing, usually resulting inhealthier children and more empowered women. Unfortunately, thesejobshaveneither lifted apparel workers outofpoverty norempowered¿hem. In fact,when women told theirmanagersat TazreenFashions they thought they shouldevacuatebecausetheyheardthefire alarm, theywere tolditwas a test andtogo backtotheir workstations .A fewmenignored themanagers and ran downthesmoke-filled stairs - justintime. Forthe womenon that secondfloor itwas toolate. Yet workers are dependingon thesejobs. In fact, manyareso desperate foremployment that theysaythatthey'd return to Tazreentomorrow ifthey could.On 30 November, theBBChadthis from a former Tazreenworker: "Wewanttheowner toreopen the factory as soonas possibleorpay us a fewmonths of salarybecausewe have nowhere elsetogo right at thismoment ",said Hasan, a worker whoescapedthe fire and usesonly onename. 7 needtorecover soon.I needmoney immediately .We want at leastfour months of salarytojustgetbynowand bythis time , we willlook for jobsinother factories", saidDipa Akter, the19-year-old worker who injured herlegescaping the fireand whohasworked at thefactory forthree years."Otherwise, I havetogo backtomyvillage, where I have nothing todo". BrandMonitoring Programmes The greattragedy behindtheseaccidents is that brandshave knowntheywere takingrisksby relying on unsafeapparelfactories that struggled toensureworker safety. Brandshavespecifically soughtto minimise thatriskbyestablishing voluntarymonitoring programmes that generate confidential reportsso brand representatives knowwhichfactories toavoid. Ironically, Walmart'smonitoring programme actually did whatitwas designedto do - itdeauthorisedTazreen Fashions before the fire. Walmart executives'insistence on makingthis pointtothepressindicates that they see nothing wrongwithwalking awayfrom problematic factorieswithoutinforming workersabout what theyfound.Were the problemstheyfoundin Tazreenrelated tofaulty electrical wiring orother fire hazards? Withthewaycorporate monitoring programmes arestructured, itis entirely possible fora brands'monitoring agentto discover a fire hazard and pull out withouttellinganyone. Global apparel companiescannotcontinueto keepthiskindofinformation confidential; inthe end thesesecret s becomedeadly. The factthattwoWalmart suppliers continued to use Tazreenafter itwas de-authorised shows thatWalmart is notin fullcontrol of itssupply chain;somebody downthechainviolated itsprotocol .Yet thebusinessmodelthatWalmart has builtis precisely intended to ensureitsdistance from theactualworkers, production, andanyreal responsibility. For the families of 112 garment workerswho died at Tazreen,however,these disclaimers don'tmatter now. Meanwhile, as Walmart executives defendthe company on thegrounds thattheir system had a glitch in it,theworkers interviewed bytheBBC makeitclearthepriority nowshouldbe on how to ensurecompensation fortheinjured and the families ofthedeceased.Thelackofpriority being given toworkers' concerns andwelfare isemblematicofwhatis fundamentally wrongwithglobal brands' approach tomonitoring their suppliers. Real Solutions - NotJustMoreofthe Same Now is a keymoment whenall consumers need to come together and demanda changein the current modelofproduction: a modelthat allows INTERNATIONAL union rights pase 10Volume 19Issue 4201 2 FOCUS □ BUSINESSAND HUMANRIGHTS globalbrandsto keep the profits and disclaim any responsibility when thingsgo wrong.In order to changetheapparelindustry, consumers need to become activists and join directaction campaigns to demanda muchmoresignificant response.We need to effect a paradigmshift wherebrandsrealisethatno one acceptstheir claims about voluntary initiatives sheathedin 'standard confidentiality agreements' anymore. Thefires area two-part problem. On one side, a technical fixis neededto rebuild infrastructure and ensurebuilding inspectors are moreskilled, morenumerous and morereliable.Butthesecond part,justas crucialas thefirst, is therelationship betweenmanagement and workers. In short, a system ofindustrial relations is crucial to establishing a levelofrespect and trust between...

Transregional Military Dimensions of Civilian Protection: A Two-Part Problem with a Two-Part Solution

The utilization of peacekeepers to protect civilians confronting devastation remains an issue of considerable debate about whether sufficient capacity exists to take on the task. This paper examines the difficulties of providing resources both for quick response civilian protection against ongoing devastation and follow-on longer-term activities that can help guarantee against a resurgence of violence. Research drawing on the CPASS database of worldwide peacekeeping operations reveals two clusters of troop contributing countries: a UN set and a cross-cutting “Western” agendas group. The fist cluster has demonstrated a willingness to deploy to long-term multidimensional peacekeeping missions that can help dampen the prospects of resurgence, and the second group (plus one important idiosyncratic actor) has demonstrated a willingness to take on usually shorter but more dangerous peace enforcement missions. For the foreseeable future, the most promising prospect for the protection of civilians involves the two clusters operating either in parallel or in sequence. While this division of labor may not be the most efficient way of doing business in an ideal world, it is the best we can expect for the world in which we live.

A coupled global registration and segmentation framework with application to magnetic resonance prostate imagery.

Extracting the prostate from magnetic resonance (MR) imagery is a challenging and important task for medical image analysis and surgical planning. We present in this work a unified shape-based framework to extract the prostate from MR prostate imagery. In many cases, shape-based segmentation is a two-part problem. First, one must properly align a set of training shapes such that any variation in shape is not due to pose. Then segmentation can be performed under the constraint of the learnt shape. However, the general registration task of prostate shapes becomes increasingly difficult due to the large variations in pose and shape in the training sets, and is not readily handled through existing techniques. Thus, the contributions of this paper are twofold. We first explicitly address the registration problem by representing the shapes of a training set as point clouds. In doing so, we are able to exploit the more global aspects of registration via a certain particle filtering based scheme. In addition, once the shapes have been registered, a cost functional is designed to incorporate both the local image statistics as well as the learnt shape prior. We provide experimental results, which include several challenging clinical data sets, to highlight the algorithm's capability of robustly handling supine/prone prostate registration and the overall segmentation task.

Diffraction of two-dimensional high-frequency electromagnetic waves by a locally perturbed two-part impedance plane

During the second half of the last century mixed boundary-value problems had been an appealing research subject for both mathematicians and engineers. Among this kind of problems those connected with wave propagation in half-spaces or slabs bounded by sectionally homogeneous boundaries took an important place because they were motivated by microwave applications. The simplest problem of this kind is the classical two-part problem which can be reduced to a functional equation involving two unknown functions, say Ψ +( ν) and Ψ −( ν), which are regular in the upper and lower halves of the complex ν-plane, respectively. This functional equation can be rigorously treated by the Wiener–Hopf technique. When the boundary consists of three (or more) parts, the resulting functional equation involves also an entire function, say P( ν), in addition to Ψ +( ν) and Ψ −( ν), which makes the problem not solvable exactly. A local (non-homogeneous) perturbation on a two-part boundary, which is of extreme importance from engineering point of view, gives also rise to a problem of this type. The known methods established to overcome the difficulties inherent to the three-part problems are based on the elimination of the entire function P( ν) first to obtain a linear system of two singular integral equations for Ψ +and Ψ −. After having determined the functions Ψ +( ν) and Ψ −( ν) by solving this system of integral equations numerically, the function P( ν) is found from the functional equation in question. Numerical solutions to the aforementioned system, which need rather hard computations, cannot provide results which are suitable to physical interpretations. The aim of the present paper is to establish a new method which is based, conversely, on the elimination of the unknown functions Ψ +( ν) and Ψ −( ν) first to obtain a linear integral equation of the first kind for the entire function P( ν), which can be solved rather easily by regularized numerical methods. Then the functions Ψ +( ν) and Ψ −( ν) are determined through the classical Wiener–Hopf technique. The result to be obtained by this approach seems to be more suitable to physical interpretations and permits one to reveal the effect of the perturbation on the scattered wave. Some illustrative examples show the applicability and effectiveness of the method.

Adjustment studies in self-consistent relativistic mean-field models

We investigate the influence of the adjustment procedure and the set of measured observables on the properties and predictive power of relativistic self-consistent mean-field models for the nuclear ground state. These studies are performed with the point-coupling variant of the relativistic mean-field model. We recommend optimal adjustment algorithms for the general two-part problem and we identify various trends and dependencies as well as deficiencies of current models. Consequences for model improvements are presented.

Trend Shift Detection in Jet Engine Gas Path Measurements Using Cascaded Recursive Median Filter With Gradient and Laplacian Edge Detector

Trend shift detection is posed as a two-part problem: filtering of the gas turbine measurement deltas followed by the use of edge detection algorithms. Measurement deltas are deviations in engine gas path measurements from a “good” baseline engine and are a key health signal used for gas turbine performance diagnostics. The measurements used in this study are exhaust gas temperature, low rotor speed, high rotor speed and fuel flow, which are called cockpit measurements and are typically found on most commercial jet engines. In this study, a cascaded recursive median (RM) filter, of increasing order, is used for the purpose of noise reduction and outlier removal, and a hybrid edge detector that uses both gradient and Laplacian of the cascaded RM filtered signal are used for the detection of step change in the measurements. Simulated results with test signals indicate that cascaded RM filters can give a noise reduction of more than 38% while preserving the essential features of the signal. The cascaded RM filter also shows excellent robustness in dealing with outliers, which are quite often found in gas turbine data, and can cause spurious trend detections. Suitable thresholding of the gradient edge detector coupled with the use of the Laplacian edge detector for cross checking can reduce the system false alarms and missed detection rate. Further reduction in the trend shift detection false alarm and missed detection rate can be achieved by selecting gas path measurements with higher signal-to-noise ratios.

A generalization of the Wiener-Hopf approach to direct and inverse scattering problems connected with non-homogeneous half-spaces bounded by n-part boundaries

The classical Wiener-Hopf method connected with mixed two-part boundary-value problems is generalized to cover n-part boundaries. To this end one starts from an ad-hoc representation for the Green function, which involves n unknown functions having certain analytical properties. Thus the problem is reduced to a functional equation involving n unknowns, which constitutes a generalization of the classical Wiener-Hopf equation in two unknowns. To solve this latter which cannot be solved exactly when n > 3, one establishes a new method permitting one to obtain the asymptotic expressions valid when the wavelength is sufficiently small as compared with the widths of the inner strips of the boundary. The essentials of the method are elucidated through a concrete inverse scattering problem whose aim is to determine the constitutive electromagnetic parameters of a slab and a half-space bounded by an n-part impedance plane. Some illustrative numerical examples show the applicability as well as the accuracy of the method.

An optimal ( Q,r) policy for a multipart assembly system under stochastic part procurement lead times

We consider an EOQ-type model for a simple production system, where a number of parts are acquired to produce a single product and the part procurement lead times are random. Assembly is instantaneous and takes place intermittently in batches but cannot start until all the parts are available. The problem is to simultaneously determine when to order each part and what lot size to produce, namely to determine the reorder point for each part and the assembly lot size, so that the average total cost per unit time, composed of the setup cost, inventory holding costs for the parts and the assembled product, and the shortage cost for the assembled product, is minimized. We then develop a tailormade solution method for this problem to obtain a global optimal solution by taking advantage of the structure of the problem formulation, where the nonlinear programming problem is decomposed into a family of subproblems parametrized by the average assembly delay time. Numerical experiments are then conducted for the case of twopart problems, and some interesting observations are made.