Probabilistic structural analysis methods for select space propulsion system components

The Probabilistic Structural Analysis Methods (PSAM) project developed at the Southwest Research Institute integrates state-of-the-art structural analysis techniques with probability theory for the design and analysis of complex large-scale engineering structures. An advanced efficient software system (NESSUS) capable of performing complex probabilistic analysis has been developed. NESSUS contains a number of software components to perform probabilistic analysis of structures. These components include: an expert system, a probabilistic finite element code, a probabilistic boundary element code and a fast probability integrator. The NESSUS software system is shown. An expert system is included to capture and utilize PSAM knowledge and experience. NESSUS/EXPERT is an interactive menu-driven expert system that provides information to assist in the use of the probabilistic finite element code NESSUS/FEM and the fast probability integrator (FPI). The expert system menu structure is summarized. The NESSUS system contains a state-of-the-art nonlinear probabilistic finite element code, NESSUS/FEM, to determine the structural response and sensitivities. A broad range of analysis capabilities and an extensive element library is present

A new displacement-based approach to calculate stress intensity factors with the boundary element method

The analysis of cracked brittle mechanical components considering linear elastic fracture mechanics is usually reduced to the evaluation of stress intensity factors (SIFs). The SIF calculation can be carried out experimentally, theoretically or numerically. Each methodology has its own advantages but the use of numerical methods has be-come very popular. Several schemes for numerical SIF calculations have been developed, the J-integral method being one of the most widely used because of its energy-like formulation. Additionally, some variations of the J-integral method, such as displacement-based methods, are also becoming popular due to their simplicity. In this work, a simple displacement-based scheme is proposed to calculate SIFs, and its performance is compared with contour integrals. These schemes are all implemented with the Boundary Element Method (BEM) in order to exploit its advantages in crack growth modelling. Some simple examples are solved with the BEM and the calculated SIF values are compared against available solutions, showing good agreement between the different schemes

Is the position of the femur tibia joint under feedback control in the walking stick insect?: II. Electrophysiological recordings

Cruse H, Pflüger H-J. Is the position of the femur tibia joint under feedback control in the walking stick insect?: II. Electrophysiological recordings. The journal of experimental biology. 1981;92(1):97-107

The contributions of diverse sense organs in the control of leg movement by a walking insect

Cruse H, Dean J, Suilmann M. The contributions of diverse sense organs in the control of leg movement by a walking insect. Journal of Comparative Physiology, A. 1984;154(5):695-705

The human arm as a redundant manipulator: the control of path and joint angles

Cruse H, Brüwer M. The human arm as a redundant manipulator: the control of path and joint angles. Biological cybernetics. 1987;57(1-2):137-144.The movements studied involved moving the tip of a pointer attached to the hand from a given starting point to a given end point in a horizontal plane. Three joints — the shoulder, elbow and wrist —were free to move. Thus the system represented a redundant manipulator. The coordination of the movements of the three joints was recorded and analyzed. The study concerned how the joints are controlled during a movement. The results are used to evaluate several current hypotheses for motor control. Basically, the incremental changes are calculated so as to move the tip of the manipulator along a straight line in the workspace. The values of the individual joints seem to be determined as follows. Starting from the initial values the incremental changes in the three joint angles represent a compromise between two criteria: 1) the amount of the angular change should be about the same in the three joints, and 2) the angular changes should minimize the total cost of the arm position as determined by cost functions defined for each joint as a function of angle. By itself, this mechanism would produce strongly curved trajectories in joint space which could include additional acceleration and deceleration in a joint. These are reduced by the influence of a third criterion which fits with the mass-spring hypothesis. Thus the path is calculated as a compromise between a straight line in workspace and a straight line in joint space. The latter can produce curved paths in the workspace such as were actually found in the experiments. A model calculation shows that these hypotheses can qualitatively describe the experimental findings

Revisiting "Tin in South-eastern Europe?"

Obnovom arheoloških iskopavanja antičkog kastela Timakum Minus 2019. godine stvorile su se nove mogućnosti za tumačenja njegovih građevina koje su istraživane pre više decenija. Među ostacima građevina oko antičkog kastela Timacum Minus-a posebnu pažnju privlači delimično istražen "objekat sa hipokaustom", naročito u pogledu njegovih konstruktivnih karakteristika. Pored inače čestih antičkih konstrukcija hipokausta i zidnog grejanja, među ostacima ove građevine uočena je i posebna vrsta građevinskih elemenata - keramičke cevi za svodove. Velika količina otkrivenih cevi ukazala je na to da je ova građevina zaista imala svodove izrađene od njih. Iako je pojava cevi za svodove prilikom istraživanja antičkih lokaliteta na tlu jugoistočne Evrope registrovana, ona nije dovoljno dokumentovana, kao što ni sama funkcija cevi često nije prepoznata. Jedan od razloga za to jeste nedovoljna upućenost istraživača u specifične karakteristike cevi za svodove i njihovu funkciju, usled čega se one mešaju sa vodovodnim cevima, tubulusima ili kalemovima vezanim za zidno grejanje - budući da svaki od tih elemenata pripada keramičkim proizvodima koji su namenjeni građevinarstvu. U radu su razmatrane karakteristike cevi za svodove na Timakum Minusu, kao i kontekst u kome su pronađene unutar "objekta sa hipokaustom". Na osnovu nalaza pečata kohorte Aurelije II Daradanorum određeno je da "objekat sa hipokaustom" i konstrukcija svodova od keramičkih cevi potiču iz III veka - u kome je i inače pojava tih svodova širom Rimskog carstva bila česta. Prilikom sistematizacije vrsta keramičkih cevi na Timakum Minusu posebno je izdvojena ona koje je bilo najviše u "objektu sa hipokaustom". U sklopu nje je prepoznat i sasvim specifičan centralni element koji je omogućavao da se dva niza cevi na istom pravcu, ali iz suprotnih smerova, međusobno spoje. Taj element je definisao oblik svoda kojim su bile pokrivene prostorije čiju je rekonstrukciju osnove bilo moguće izvršiti. Arhitektonske analize "objekta sa hipokaustom", kao i karakteristike uočene na samim cevima ukazale su na to da su prostorije bile pokrivene poluobličastim svodom, izgrađenim od lučnih vertikalnih nizova cevi koje su u temenu bile ,,zaključane" centralnim elementom. Rekonstrukcija izgleda cevi i načina njihovog ređanja uklapa se u hronologiju izvođenja objekta i svoda tokom III veka. Daljim statičkim analizama došlo se do još nekoliko saznanja. Pokazalo se da je preko svoda morao biti nanesen određen sloj malterne mase da bi debljina svoda dosegla optimalnu vrednost u opsegu 20-30 cm. Na osnovu proporcija objekta koje su određene u njegovoj osnovi ispitana je visina objekta, gde je grupa slučajeva takođe definisana proporcionalno. Prema našim analizama, zidovi prostorija "objekta sa hipokaustom" u kojima su cevi registrovane mogli su dosezati visinu do 3,08 m, dok je visina prostorija u temenu svoda mogla biti 6,16 m. Ovim istraživanjem pokušali smo da ukažemo na veliki značaj pojedinačnih arhitektonsko-građevinskih elemenata, a među njima i keramičkih cevi za svodove, kojima se često ne pridaje dovoljna pažnja. Nalazi keramičkih cevi za svodove u Timakum Minusu, uz izvršene arhitektonske analize, upotpunjuju sliku otkrivenog "objekta sa hipokaustom" iz više aspekata. Posebno je značajno definisanje njegove visine, koje je veoma teško za antičke građevine profane arhitekture na našem tlu budući da su najčešće sačuvane u prizemnoj ili temeljnoj zoni. Značaj nalaza keramičkih cevi za svodove u Timakum Minusu veliki je stoga što je on omogućio kako konkretno definisanje konteksta njihovog nalaza tako i rekonstrukciju oblika određenih delova građevine pomoću tog elementa, što do sada nije istraživano prilikom analiza antičke arhitekture na tlu jugoistočne Evrope.The important role of the Balkans in the origin and development of metallurgy is well established with respect to copper. In addition, Aleksandar Durman, in his 1997 paper "Tin in South-eastern Europe?", essentially initiated studies into the role of the Balkans in Europe's Bronze Age tin economy. He identified six geologically favourable sites for tin mineralisation and associated fluvial placer deposits in the former Yugoslavian republics, and suggested that these may have added to the tin supply of the region. The viability of two of these sites has been confirmed (Mt Cer and Bukulja, Serbia) but the exploitation potential for the other locations has remained untested. River gravels from these four sites (Motajica and Prosara in Bosnia and Herzegovina; Bujanovac in Serbia; Ogražden in North Macedonia) were obtained by stream sluicing and panning. The sites of Prosara and Bujanovac were found to be barren with respect to cassiterite (SnO 2). Streams flowing from Motajica and Ogražden were both found to contain cassiterite, but in amounts several orders of magnitude less than at Mt Cer and Bukulja. Although it is possible that minor tin recovery occurred at Motajica and Ogražden, it is unlikely that they could have contributed meaningfully to regional tin trade. This is supported by the fact that the isotopic signature (d 124 Sn) of cassiterite from Motajica is highly enriched in light isotopes of tin compared to that associated with Late Bronze Age artefacts of the region

Structural reliability methods: Code development status

The Probabilistic Structures Analysis Method (PSAM) program integrates state of the art probabilistic algorithms with structural analysis methods in order to quantify the behavior of Space Shuttle Main Engine structures subject to uncertain loadings, boundary conditions, material parameters, and geometric conditions. An advanced, efficient probabilistic structural analysis software program, NESSUS (Numerical Evaluation of Stochastic Structures Under Stress) was developed as a deliverable. NESSUS contains a number of integrated software components to perform probabilistic analysis of complex structures. A nonlinear finite element module NESSUS/FEM is used to model the structure and obtain structural sensitivities. Some of the capabilities of NESSUS/FEM are shown. A Fast Probability Integration module NESSUS/FPI estimates the probability given the structural sensitivities. A driver module, PFEM, couples the FEM and FPI. NESSUS, version 5.0, addresses component reliability, resistance, and risk

A Comparative Study of the ReCell® Device and Autologous Spit-Thickness Meshed Skin Graft in the Treatment of Acute Burn Injuries.

Early excision and autografting are standard care for deeper burns. However, donor sites are a source of significant morbidity. To address this, the ReCell® Autologous Cell Harvesting Device (ReCell) was designed for use at the point-of-care to prepare a noncultured, autologous skin cell suspension (ASCS) capable of epidermal regeneration using minimal donor skin. A prospective study was conducted to evaluate the clinical performance of ReCell vs meshed split-thickness skin grafts (STSG, Control) for the treatment of deep partial-thickness burns. Effectiveness measures were assessed to 1 year for both ASCS and Control treatment sites and donor sites, including the incidence of healing, scarring, and pain. At 4 weeks, 98% of the ASCS-treated sites were healed compared with 100% of the Controls. Pain and assessments of scarring at the treatment sites were reported to be similar between groups. Significant differences were observed between ReCell and Control donor sites. The mean ReCell donor area was approximately 40 times smaller than that of the Control (P < .0001), and after 1 week, significantly more ReCell donor sites were healed than Controls (P = .04). Over the first 16 weeks, patients reported significantly less pain at the ReCell donor sites compared with Controls (P ≤ .05 at each time point). Long-term patients reported higher satisfaction with ReCell donor site outcomes compared with the Controls. This study provides evidence that the treatment of deep partial-thickness burns with ASCS results in comparable healing, with significantly reduced donor site size and pain and improved appearance relative to STSG