The NavBelt-a computerized travel aid for the blind based on mobilerobotics technology

This paper presents a new concept for a travel aid for the blind. A prototype device, called the NavBelt, was developed to test this concept. The device can be used as a primary or secondary aid, and consists of a portable computer, ultrasonic sensors, and stereophonic headphone. The computer applies navigation and obstacle avoidance technologies that were developed originally for mobile robots. The computer then uses a stereophonic imaging technique to process the signals from the ultrasonic sensors and relays their information to the user via stereophonic headphones. The user can interpret the information as an acoustic “picture” of the surroundings, or, depending on the operational mode, as the recommended travel direction. The acoustic signals are transmitted as discrete beeps or continuous sounds. Experimental results with the NavBelt simulator and a portable prototype show that users can travel safely in an unfamiliar and cluttered environment at speeds of up to 0.8 m/s     

The Effects of Thermal Treatment on Associations between Fatty Acids and Montmorillonite

The sorption from CCl₄ solutions of acetic, lauric and stearic acids by montmorillonites saturated with H, Li, Na, K, Cs, Ca, Mg, Cu, Al and Fe, was studied by IR and X-ray methods combined with various thermal treatments. Two distinct species were detected in the clay phase, the carboxylic acid (RCOOH) and the carboxylate anion (RCOO⁻). The ratios of the two sorbed species were found to be dependent both on the nature of the exchangeable cation and on the chain length of the acid. In Al⁻, Fe⁻ and Cu—montmorillonites, the ionic species predominates whereas in Cs—montmorillonite the acidic species predominates. Stearic acid shows the highest tendency to dissociate. The following associations were identified as occurring in the interlayer space: (I) and (II) — linkages between COOH group and oxygen sheet of silicate layer or with hydrophobic structured water; (III) — linkage between a COOH group and an exchangeable cation through a “water bridge”; (IV) — direct linkage between a COOH group and an exchangeable cation; (V) — linkage between a COO⁻ group and an exchangeable cation through a “water bridge” and (VI) — direct linkage between a COO⁻ group and an exchangeable cation. Although several types of associations are associated with every homoionic montmorillonite, some are more predominant. Thus, with Cs, association (I) predominates. With Li, Ca and Mg, association (III) predominates and is transformed to (IV) after thermal dehydration; whereas with Na and K association (IV) appears in freshly prepared sample. Al, Fe and Cu—montmorillonites mainly produce association (V). This structure is transformed into (VI) in the case of Al—montmorillonite by stearic and lauric acids, only. In the case of Cu—montmorillonite, all the three acids are transformed into (VI), but at 200°C decarboxylation of lauric and stearic acids occur.     

Identification of the thermal phases in firing of kaolinite to mullite by using micro-Raman spectroscopy and curve-fitting

Firing of kaolinite to mullite is an important process in ceramic industry. In the present study, Raman spectroscopy and curve-fitting are utilized for identification of the thermal phases in progressive firing of kaolinite to mullite up to 1300 °C. The results are compared to that observed by XRD. Many natural kaolinites consist of accessory anatase, and this mineral has strong Raman bands. Therefore, the spectra of anatase-free and anatase-containing kaolinites were analyzed. The Raman response is sensitive to the degree of the structural order of the thermal phases. Dehydroxylated kaolinite is detected at 500 °C by the disappearance of the Raman bands of the kaolinite. The metakaolinite at 700 °C and the spinel-type phase at 1000 °C have broad and weak Raman bands due to their short-range and poorly-order structure, respectively. Amorphous silica is observed at 1000 °C by the development of diagnostic broad and weak Raman bands. Mullite and cristobalite are detected at 1300 °C by the appearance of characteristic Raman bands. In firing of anatase-containing kaolinite, progressive thermal transform from anatase to rutile is observed at 1100–1300 °C by the appearance of Raman bands of rutile and by the decreasing of the anatase bands. The results can be applied in using micro-Raman spectroscopy as a non-destructive method for identification of thermal phases in the composition of modern and ancient ceramic.     

Auditory guidance with the Navbelt-a computerized travel aid forthe blind

A blind traveler walking through an unfamiliar environment and a mobile robot navigating through a cluttered environment have an important feature in common: both have the kinematic ability to perform the motion, but they are dependent on a sensory system to detect and avoid obstacles. The paper describes the use of a mobile robot obstacle avoidance system as a guidance device for blind and visually impaired people. Just as electronic signals are sent to a mobile robot's motion controllers, auditory signals can guide the blind traveler around obstacles, or alternatively, they can provide an “acoustic image” of the surroundings. The concept has been implemented and tested in a new travel aid for the blind, called the Navbelt. The Navbelt introduces two new concepts to electronic travel aids (ETA's) for the blind: it provides information not only about obstacles along the traveled path, but also assists the user in selecting the preferred travel path. In addition, the level of assistance can be automatically adjusted according to changes in the environment and the user's needs and capabilities. Experimental results conducted with the Navbelt simulator and a portable experimental prototype are presented     

Fast evaluation of cutting forces in milling, applying no approximate models

A new method for fast evaluation of cutting forces in milling is introduced and tested experimentally. Unlike all existing procedures, which include the use of cutting models and approximate assumptions, in this method, the elementary functions of the cutting force are obtained from measured values only.The basic force functions for the whole feed range are acquired from one experiment using a single-tooth full-diameter (slot) milling, applying a specially developed procedure. The milling experiment is conducted under low-impact conditions, enabling accurate measurement and convenient signal processing. The basic force functions are then integrated and superimposed, using known procedures, to combine the total force in any multitooth milling combination. In this work the method is explained and tested experimentally.The suggested method enables a reliable evaluation of the cutting forces, while demanding minimal experimental work, the method applies to cutters having complicated edge geometry, and to high speed milling.Nomenclature a radial depth of cut 0<a<D - feed per tooth ratio 0<1 - d axial depth of cut - D cutter diameter - a/D radial depth ratio - cutter rotation angle - cutter rotation angle [6] - F _x,y,z() instantaneous edge cutting forces in fixture coordinates - F _t,r,z() instantaneous edge cutting forces in tool coordinates - F _x,y,z ^* F_t,r,z tool cutting force components on a multitooth cutter - h instantaneous chip thickness [6] - h* equivalent edge coefficient [6] - r ₁,r ₂ tangential radial ratio coefficient [6] - K _T tangential specific cutting force [4] - K _R radial specific cutting force [4] - N number of teeth - R _r resolution reduction factor - t instantaneous chip thickness - S ₁,S feed per tooth     

Automatic Palletizing of Concrete Pavement Blocks: An Algorithm for Near-Optimal Assembly

Palletizing concrete pavement blocks is a labor-intensive task that requires high levels of workmanship, skill, and concentration. This article proposes an automatic system in which palettes with required design patterns are assembled automatically off-site and then shipped to the construction site. The efficiency of the assembly process can be improved by incorporating automatic equipment consisting of assembly heads and feeders. An algorithm was developed to determine the optimal layout of the feeders (of different blocks) around the palette and the exact assembly sequence of each layer of blocks. Experimental results show that the algorithm is near optimal and that the solutions provided by it reduce palletizing cycle time for various patterns and sizes of concrete block by 20 to 30 percent.     

Post-war reconstruction and conservation of the historic Jewish Quarter in Jerusalem, 1967–1975

The aim of this paper is to examine post-war planning and reconstruction of the historic Jewish Quarter of the Old City of Jerusalem from 1967 to 1975. It focuses on the role of conservation of cultural heritage in determining the quarter's character, on the interaction between ‘top-down’ national and municipal planning and grassroots initiatives, on deviations from planning and declared policies, and on historical and geographical factors affecting restoration. Public opinion, individual initiatives, and response to immediate needs were more decisive in determining the character of the reconstruction than much of the planning. Intentional and unanticipated spatial changes within the Jewish Quarter and in its relationships with surrounding areas had a particularly profound effect on its character.