采用气雾化Zn-22%Al粉末挤压制造微型螺旋齿轮(英文)

基于Zn-22%Al共析合金的超塑性,采用粉末挤压工艺制造微型螺旋齿轮,以减小成形压力和获得细小的显微组织。该螺旋齿轮的规格为:模数0.3,齿数1.2,螺旋角15°。将粉末压制坯通过烧结和固溶热处理进行致密化。致密化的坯料由层状和细晶状组织组成。在温度250°C,应变速率2.36×10-3和1.18×10-1s-1的条件下对坯料进行挤压,并对挤压成形的螺旋齿轮的力学性能进行测试。     

Thermodynamic evaluation of oxygen behavior in Ti powder deoxidized by Ca reductant

To produce low oxygen Ti powder of less than 1000 mass ppm, commercial Ti powder was deoxidized by two types of Ca reductants: a solid Ca and a Ca vapor. Compared with the iso-oxygen partial pressure in the Ti-O binary phase diagram, the P_O2 in the raw Ti powder increased with temperature compared to the reduction reaction of Ca. Therefore, the O₂ content in the Ti powder decreased as the deoxidation temperature increased from 873 K, showing a local minima at 1273 K. The oxygen concentration at 1373 K was greater than that at 1273 K because the oxygen solubility of the Ti powder was increased by the equilibrium relation between Ca and CaO. On the basis of the thermodynamic assessment, the deoxidation of Ti powder can be improved by increasing the temperature and lowering the oxygen solubility with the saturation of CaO.     

Deoxidation and subsequent densification of sintered titanium by Ca deoxidizer

In this study, a sintering process involving simultaneous deoxidation and sintering was developed, using the vapor of a deoxidizer (Ca) to produce low-oxygen, high-density titanium. Compared to a series of reference titanium powder samples, the bodies sintered with Ca exposure had an ～1,400 ppm lower oxygen content, resulting in an ～2% increase in their density. This appears to be the result of decreased surface oxidation on the titanium, as increased oxidation suppresses densification at high sintering temperatures. The effect of the Ca deoxidizer was a lower oxidation, thereby increasing the sintered density. The Vickers hardness of sintered bodies from both experiments increased from an initial value of ～249 Hv at 900 °C to ～286 Hv at 1,400 °C, respectively. Moreover, both experiments revealed a tensile strength of ～170 MPa at 900 °C that finally increased to ～218 MPa at 1,400 °C. Meanwhile, the bodies sintered with Ca, the elongation was on average over 1% higher than contrary samples.     

Effect of α-lath size on the mechanical properties of Ti–6Al–4V using core time hydrogen heat treatment

ABSTRACT

When hydrogen is dissolved, brittleness occurs in the material. However, in the case of titanium and titanium alloy, hydrogen can be temporarily dissolved and removed, thereby improving the mechanical properties of titanium and titanium alloy. In this study, Core time Hydrogen Heat treatment (CHH) applies to Ti–6Al–4V alloy to improve mechanical properties. CHH was performed at 800°C and 1000°C for 2?h. Thereafter, dehydrogenation was performed for 2 h at 700°C in vacuum atmosphere to remove residual hydrogen. After the CHH at 800°C, it was found that the α-lath size in the Ti–6Al–4V was narrowed; thereby increasing the Vickers hardness and tensile strength without decreasing in elongation.     

Effect of barrier layers on the properties of indium tin oxide thin films on soda lime glass substrates

In this paper, the electrical, structural and optical properties of indium tin oxide (ITO) films deposited on soda lime glass (SLG) haven been investigated, along with high strain point glass (HSPG) substrate, through radio frequency magnetron sputtering using a ceramic target (In₂O₃:SnO₂, 90:10 wt.%). The ITO films deposited on the SLG show a high electrical resistivity and structural defects compared with those deposited on HSPG due to the Na ions from the SLG diffusing to the ITO film by annealing. However, these properties can be improved by intercalating a barrier layer of SiO₂ or Al₂O₃ between the ITO film and the SLG substrate. SIMS analysis has confirmed that the barrier layer inhibits the Na ion's diffusion from the SLG. In particular, the ITO films deposited on the Al₂O₃ barrier layer, show better properties than those deposited on the SiO₂ barrier layer.     

Towards a cultural user interface generation principles

As ubiquitous computing, and pervasive computing technology are being applied rapidly to the service industry, in the field of HCI, more complex and in-depth research are required at the moment. The efforts to make user experience more valuable using useful multimedia technologies around us, are being made in various parts of the world. In addition to this, generation studies for developing easier and faster UI are being conducted in the field of UI. Until now, the studies have been focused on generation studies using UI pattern models, but smart UI generation development, considering the cultural environment of users, is required. The purpose of this study is to suggest 3-D integrated design principles of modeling, design, and system for the design of cultural user interface generation reflecting the users’ potential culture models. For this, a CTT model was designed based on MB-UID; and a cultural UI generation system architecture was designed by using cultural dimension models and cultural markers. To analyze the cultural factors, CISC (Cultural Index Score for Country) was derived in the process of culture profiling. Then, to verify the design model, culture UI was implemented, targeting the category UI of smartphone app stores.     

Model matching inclusion for input/state asynchronous sequential machines

The problem of model matching for asynchronous sequential machines consists of finding a feedback controller for a given open-loop machine so that the resulting closed-loop machine matches a desired model. In this paper, the control objective is extended to model matching inclusion in which the behavior of the closed-loop system should be contained in that of the model. The supremal controllable sub-model is characterized as an asynchronous machine with the largest behavior set contained in a given model that can be matched by the closed-loop machine via state feedback control. An effective computational algorithm is developed and an example is provided for illustration.     

Allocation of QoS connections in MF-TDMA satellite systems: a two-phase approach

We address the problem of providing guaranteed quality-of-service (QoS) connections over a multifrequency time-division multiple-access (MF-TDMA) system that employs differential phase-shift keying (DPSK) with various modulation modes. The problem can be divided into two parts-resource calculation and resource allocation. We present algorithms for performing these two tasks and evaluate their performance in the case of a Milstar extremely high frequency satellite communication (EHF-SATCOM) system. In the resource-calculation phase, we calculate the minimum number of timeslots required to provide the desired level of bit-error rate (BER) and data rate. The BER is directly affected by the disturbance in the link parameters. We use a Markov modeling technique to predict the worst case disturbance over the connection duration. The Markov model is trained offline to generate a transition-probability matrix, which is then used for predicting the worst case disturbance level. We provide simulation results to demonstrate that our scheme outperforms the scheme currently implemented in the EHF-SATCOM system. The resource-allocation phase addresses the problem of allocating actual timeslots in the MF-TDMA channel structure (MTCS). If we view the MTCS as a collection of bins, then the allocation of the timeslots can be considered as a variant of the dynamic bin-packing problem. Because the this problem is known to be NP-complete, obtaining an optimal packing scheme requires a prohibitive amount of computation. We propose a novel packing heuristic called reserve channel with priority (RCP) fit and show that it outperforms two common bin-packing heuristics.     

Checkpoint Management with Double Modular Redundancy Based on the Probability of Task Completion

This paper proposes a checkpoint rollback strategy for real-time systems with double modular redundancy.Without built-in fault-detection and spare processors,our scheme is able to recover from both transient and permanent faults.Two comparisons are conducted at each checkpoint.First,the states stored in two consecutive checkpoints of one processor are compared for checking integrity of the processor.The states of two processors are also compared for detecting faults and the system rolls back to the previous checkpoint whenever required by logic of the proposed scheme.A Markov model is induced by the fault recovery scheme and analyzed to provide the probability of task completion within its deadline.The optimal number of checkpoints is selected so as to maximize the probability of task completion.