User experimentation: an evaluation of velocity control techniques in immersive virtual environments

While many of the existing velocity control techniques are well designed, the techniques are often application-specific, making it difficult to compare their effectiveness. In this paper, we evaluate five known velocity control techniques using the same experimental settings. We compare the techniques based on the assumption that a good travel technique should be easy to learn and easy to use, should cause the user to have few collisions with the VE, should allow the user to complete tasks faster, and should promote better recollection of the environment afterwards. In our experiments, we ask twenty users to use each velocity control technique to navigate through virtual corridors while performing information-gathering tasks. In all cases, the users use pointing to indicate the direction of travel. We then measure the users’ ability to recollect the information they see in the VE, as well as how much time they spend in the VE and how often they collide with the virtual walls. After each test, we use questionnaires to evaluate the ease of learning and ease of use of the velocity control technique, and the users’ sense of presence in the environment. Each of the travel techniques is then evaluated based on the users’ performances in the VE and the results of their questionnaires.     

Determination of Cutting-Condition-Independent Coefficients and Runout Parameters in Ball-End Milling

This paper presents a systematic and practical method for determining cutting-condition-independent coefficients in ball-end milling. An approach for estimating the runout offset and its location angle is also described based on a single cutting force measurement. An in-depth analysis of the characteristics of these cutting coefficients, which can be determined from only a few test cuts, is provided. The size effect is also modelled, including the characteristics of the ball-end mill geometry, and incorporated into the cutting force model. This method of estimating the 3D ball-end milling force coefficients was tested experimentally for various cutting conditions and gave excellent cutting force predictions. Also, the estimated values of the runout offset agreed well with the measurements.     

Hydrometallurgical Process for Copper Recovery from Waste Printed Circuit Boards (PCBs)

Present paper focuses on the selective recovery of copper from the enriched ground printed circuit boards (PCBs) using leaching and solvent extraction. The metal-enriched ground sample obtained from the beneficiation of the sized PCBs in a laboratory scale column type air separator contained mainly 49.3% Cu, 3.83% Fe, 1.51% Ni, 5.45% Sn, 4.71% Pb, and 1.85% Zn. The leaching of the enriched sample with 3.5 mol/L nitric acid dissolved 99% copper along with other metals at 323 K temperature and 120 g/L pulp density in 1 h time. The composition of the leach liquor with wash solution was found to be 42.11 g/L Cu, 2.12 g/L Fe, 4.02 g/L Pb, 1.58 g/L Zn, and 0.4 g/L Ni. The McCabe–Thiele plot indicated the requirements of three counter-current stages for maximum extraction of copper from the leach liquor at pH 1.5 using 30, 40, and 50% (v/v) LIX 984 N at the phase ratios (A/O) of 1:3, 1:2, and 1:1.5, respectively. The counter-current simulation studies show the selective extraction of 99.7% copper from the leach liquor feed of 1.5 pH in three stages with 50% LIX 984 N at A/O phase ratio of 1:1.5. The stripping of copper from the loaded organic with sulfuric acid produced copper sulfate solution from which copper metal/powder could be recovered by electrolysis/ hydrogen reduction.     

Influence of steam injection and hot gas bypass on the performance and operation of a combined heat and power system using a recuperative cycle gas turbine

The influence of steam injection and hot gas bypass on the performance and operation of a combined heat and power (CHP) system using a recuperative cycle gas turbine was investigated. A full off-design analysis was used to investigate not only the change in performance but also the variation in engine operation caused by steam injection. The performance improvement capability and operating limitations of full steam injection was examined. Selected operations (partial steam injection and underfiring) that secure minimum compressor surge margin were comparatively analyzed. Partial steam injection was found to be a better option than underfiring in all thermodynamic aspects. Under ISO condition, power and efficiency improvements in the partial injection targeted at a 10% surge margin are 27% and 7.4%, respectively. This study also investigated the increase in steam generation brought by the bypass of turbine exhaust gas around the recuperator. This bypass provided high operational flexibility by varying the capacity of thermal energy supply in both the pure CHP operation and the steam-injected operation. In particular, in the steam-injected operation, the capacity of thermal energy supply can be largely increased by the said bypass, while producing a greater power output than the pure CHP system.     

Interactive wireless virtual colonoscopy

We present an interactive virtual colon navigation system on a PDA that is a client-server system over a wireless network. For improving the quality of the rendering results on the PDA, the overall rendering speed, and the user interactivity, we propose three novel methods and adapt a GPU-based direct volume rendering technique. Using these proposed methods, our system can support approximately a two times faster navigation speed and 17 percent better PSNR than previous remote visualization methods with a 512×512×361 volumetric colon CT data using a PDA device over 802.11b wireless network.