Hidden Material Research Articles

Afterword: hidden beauty

People love a secret, as long as they are in on it. One might even argue that historians are more attracted to secrecy than the average scholar, or average individual, in that the tools we have for unearthing documentation from the past regularly trawl up long-dormant secrets. At one time, someone may have died to preserve this secret; for me, it is lying accessible in an archive. The challenge is not reading the secret – it is crafting an argument and a narrative that would make others care for this once tightly-held confidence. This fascination of access to privileged information, to being (whether licitly or not) in the know, and the rich texture that hidden material provides, partly explains the recurrent historiographical attention to secrecy. Historians get to have both secrecy and transparency at once, at least in many cases where the precious documents survive and are not still locked behind the classificatory walls of national-security states or profit-seeking megacorporations.

Lives on the Line

Being prepared to die for one's country has long been the touchstone of nationalism. But as the confused debates about Britishness have indicated over the last decade, concepts of national identity in the UK have been eroding fast and there is a growing uncertainty about what it means to serve one's country. The figure of the soldier is ubiquitous throughout the media, but the image of the flag-draped coffin remains a site of intense struggle, not just over the meanings of military sacrifice but also the perceived value of the war in which the individual soldier 'gave' their life. The response of different European electorates to the NATO-led ISAF operation in Afghanistan shows how governments can be vulnerable to the political risks inherent in committing their countries to war. Managing these risks entails controlling the representation of harm experienced not just by civilians (including torture and abuse of detainees) in the war zone but also by serving military personnel being deployed. Paying close attention to the figure of the soldier as a particular kind of worker-citizen can expose the hidden material and financial resources required to commit the country to war. It can also provide a focus for tracking the ideological energy involved both in securing public acquiescence and in marginalising opposition as a form of disloyalty to the national state.

Numerical simulation of two-dimensional problems of creep crack growth with material damage consideration

Approach for numerical simulation of the process of the creep crack growth taking into account the hidden material damage is proposed. The approach is based on the application of finite element creep modeling, accompanied by damage. For calculations, the FEM Creep software package is used. Using the proposed algorithm for rebuilding the grid with the removal of the destroyed elements, the current picture of deformation and fracture is analyzed. This takes into account the growing level of damage during the crack motion in each element. Numerical fracture simulation data are used to determine the constants in the differential creep fracture propagation equation. As an example, the creep fracture of planar specimens with sharp notches in their plane is considered. The material of the specimens is a high-temperature nickel-based alloy EI 867 at a temperature of 950 °C. Calculations are carried out for different values of the load. For different times, finite element grids with remote elements are shown. Graphs of the dependence of crack length on time are built. Comparison of numerical and calculated data obtained with the motion equation of a crack shows their acceptable coincidence. The possibility of using the proposed approach for obtaining constants in the equation of crack motion as an alternative to the existing experimental one is discussed.

LOI-Based Pulsed Eddy Current Evaluation of Hidden Material Degradation in Coated Nonmagnetic Conductors

Abstract Coated nonmagnetic conductors are subject to material degradation hidden under nonmetallic coating. It is formidable to evaluate the degradation degree and thickness of degradation region without removing the non-conductive coating. In light of this, in this paper the feasibility of pulsed eddy current (PEC) probes for nondestructive assessment of hidden material degradation in coated nonmagnetic conductors was investigated. The characteristics of lift-off intersection (LOI) of signals from PEC probes were utilized in a bid to cancel out the influence of coating thickness on signals. A fast inverse scheme based on LOI was proposed, along with the probe to implement simultaneous evaluation of the degradation degree and thickness. A series of experiments revealed that the proposed probe is high-efficiency and capable of assessing hidden material degradation without much loss of accuracy.

Accurate Permittivity Measurements for Microwave Imaging via Ultra-Wideband Removal of Spurious Reflectors

The use of microwave imaging is becoming more prevalent for detection of interior hidden defects in manufactured and packaged materials. In applications for detection of hidden moisture, microwave tomography can be used to image the material and then perform an inverse calculation to derive an estimate of the variability of the hidden material, such internal moisture, thereby alerting personnel to damaging levels of the hidden moisture before material degradation occurs. One impediment to this type of imaging occurs with nearby objects create strong reflections that create destructive and constructive interference, at the receiver, as the material is conveyed past the imaging antenna array. In an effort to remove the influence of the reflectors, such as metal bale ties, research was conducted to develop an algorithm for removal of the influence of the local proximity reflectors from the microwave images. This research effort produced a technique, based upon the use of ultra-wideband signals, for the removal of spurious reflections created by local proximity reflectors. This improvement enables accurate microwave measurements of moisture in such products as cotton bales, as well as other physical properties such as density or material composition. The proposed algorithm was shown to reduce errors by a 4:1 ratio and is an enabling technology for imaging applications in the presence of metal bale ties.

The hidden material culture of the Dark Ages. Early medieval ceramics at Sagalassos (Turkey): new evidence (ca AD 650–800)

AbstractOn the basis of recent archaeological evidence unearthed in the course of systematic excavations by the Sagalassos Archaeological Research Project (Katholieke Universiteit Leuven) in southwestern Turkey, this paper attempts to pull together different strings of ceramic data in order to bridge the era between late antiquity and the Middle Ages (mid seventh century to ninth century AD). Our aim is to present samples of the ceramic assemblages excavated at the site of ancient Sagalassos from layers that are most probably dated to the late seventh and eighth centuries. An attempt has been made to examine rigorously the stratigraphy and its contents that are admittedly completely different to the known ceramic forms of the late Roman/early Byzantine (fourth century to mid seventh century) and middle Byzantine (early tenth century to mid 13th century) periods at Sagalassos. Five different pottery types are presented, both kitchenwares and tablewares. The fact that all the ware types presented here are local products should not be seen necessarily as a result of a general decline in trade, rural and/or urban life, but rather as a local response to a generally changing economic system and an emerging local pottery tradition based on household-organised production. The shift from the Roman mass-produced and customised wares (that started to disappear from the market) to non-specialised local/regional production (that started to satisfy basic household needs) need not have been a sudden one. Our ultimate aim is to contribute to recent attempts to throw more light on the archaeologically ‘hidden’ material culture of the so-called ‘Dark Ages’.

Archimedes brought to light

Just over 100 years ago in the summer of 1906, a Danish scholar called Johan Ludvig Heiberg travelled to the famous Metochion library of the Church of the Holy Sepulcher in Constantinople. He had got wind of an intriguing medieval prayer book that had recently been found at the library, and which contained a series of Christian prayers written on parchment recycled from older books. But underneath the scrawlings of a 13th-century medieval monk, the battered manuscript also appeared to contain some strange Greek writing as well as mysterious drawings and mathematical symbols. When Heiberg saw the book, he soon realized that the hidden material in fact contained the thoughts of Archimedes of Syracuse (287–212 BC) – one of the greatest thinkers of the ancient world.

Jet-driven molecular outflows from class 0 sources: younger and stronger than they seem?

Context. The momentum, age and momentum injection rate (thrust) of molecular outflows are key parameters in theories of star formation. Systematic biases in these quantities as inferred from CO line observations are introduced through simplified calculations. These biases were quantified for radially expanding flows. However, recent studies suggest that the youngest outflows may be better described by jet-driven bowshocks, where additional biases are expected. Aims. We investigate quantitatively the biases in momentum, age, and thrust estimates in the case of young jet-driven molecular outflows, and propose more accurate methods of determining these quantities. Methods. We use long-duration (1500 yr) high resolution numerical simulations in concert with the standard observational methods of inferring the relevant quantities to quantify the systematic biases in these calculations introduced, in particular, by dissociation, erroneous inclusion of transverse momentum, and hidden material at cloud velocity. Jet/ambient density contrasts of 0.1–1 are considered, leading to bow speeds of 60–135 km s −1 . Results. When mass-weighted velocities are used, lifetimes are overestimated by typically an order of magnitude. The molecular thrust is then underestimated by similar amounts. Using the maximum velocity in CO profiles gives better results, if empirical corrections for inclination are applied. We propose a new method of calculating the lifetime of an outflow which dramatically improves estimates of age and molecular thrust independent of inclination. Our results are applicable to younger flows which have not broken out of their parent cloud. Conclusions. Published correlations between the molecular flow thrust and the source bolometric luminosity obtained with the maximum CO velocity method should remain valid. However, dissociation at the bow head may cause the observable thrust to underestimate the total flow thrust by a factor of up to 2–4, depending on the bow propagation speed and the magnetic field strength. Detailed evaluation of this effect would greatly help to better constrain the efficiency of the ejection mechanism in protostars.

The Archival Back Burner: Manuscript Collections and the National Archives

ABSTRACT Greater access to archival materials remains a significant challenge to archivists, librarians, and researchers. In addition to official records documenting governmental activities and agencies, the National Archives and Records Administration (NARA) has significant collections of donated personal papers. Some are processed, some are in the backlog, but nearly all of the non-Presidential Library manuscript collections are inaccessible. This essay reviews the history and some of the contents of the former Record Group 200: Records of the National Archives Gift Collection, as an example of the importance of hidden material at NARA. After a contextual history of the agency and the creation of this forgotten record group, this article describes ten manuscript collections from the former RG 200 to demonstrate not only the research potential of each but show the varied nature of these materials. This study reveals the importance of access, description, and reevaluation when archivists deal with back burner collections.

Interpretive Work in Milieu Groups

Interpretive work in milieu psychotherapy groups aims to bring concealed and hidden material to the fore so that it can be discussed openly. A host of clinically important issues thrive in the milieu, about which the patients are fully aware, but are unable to discuss. Two types of interventions are described whose goal is to overcome resistance to discussion; they are clarifying interpretations and making a parallel statement. Clarifying statements help patients understand their experience in the milieu; they are interpretive when they bring avoided material into the open. In those instances where resistance to discussion is great, the subject first appears in metaphor, is worked with, and then emerges in a displaced form. Working indirectly with metaphor and displaced material can serve to overcome transference resistance. The therapist then need only ask a direct question or make a statement in order for the avoided material to emerge. The combination of working with displaced material followed by a question or statement that is framed in terms of that theme has an interpretative function.