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emission nature, the hydrogen is receiving significant attentions as a renewable energy alternative. [2,3] The electrocatalytic water splitting, consisted of the half-reaction of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), is an appealing approach for the generation of ultra-fine hydrogen with the zero-carbon emission nature and recyclability as compared with the other hydrogen generation approaches of gasification, gas reforming, renewable liquid reforming, etc. [4] To date, the Pt/Pd and IrO 2 /RuO 2 set the benchmark electrocatalysts for the HER and OER with the low overpotentials due to their excellent water-splitting capabilities. Nevertheless, their high costs make the large-scale implementation of hydrogen generation pricier and thus the development of highly efficient and stable electrocatalysts at affordable costs still remains to be one of the major challenges for the comprehensive application of green hydrogen production by the electrochemical water splitting (WS). The transition metal-based electrocatalysts with the d-orbital characteristics, i.e., Co, Ni, Cu, Fe, Mo, W, Mn, Cr, etc., have been widely explored as the electrolytic electrode alternatives with the superb HER and OER reaction capabilities and abundance on the earth crust. [5][6][7][8] The transition metals have been frequently compounded with the nonmetallic phosphide, sulfide, nitride, etc., and significant advances have been made along with the outstanding WS performances due to their superb intrinsic HER/OER reaction capabilities. [9][10][11][12] Meantime, the Co and Mn have demonstrated outstanding electron transportability and absorption of hydrogen protons and hydroxyl species. [9][10][11][12] For instance, the CoNi-MOF exhibited a low overpotential due the rapid electron transfer rate facilitated by the adequate Co incorporation. [9] The Mn-doped Ni 2 P microflowers demonstrated a low cell voltage due to the improved conductivity and increased electrochemical active sites by the incorporation of Mn. [10] The combination of Co and Mn with the nonmetallic elements of methylidyne and selenide groups such as CoMnCH and CoMnSe has demonstrated improved intrinsic characteristics for the WS. [11,12] More recently, the boron (B) is being considered as another useful nonmetallic element for The development of highly efficient and stable electrocatalysts at an affordable cost is an essential component for the large-scale implementation of green hydrogen production. In this work, the fabrication of porous CoMnB electrocatalyst is demonstrated with the incorporation of boron into the Co-Mn matrix by an electrochemical approach for bifunctional water electrocatalysis for the first time. The optimized CoMnB electrocatalyst demonstrates an excellent bifunctionality with a low 2-E turnover voltage of 1.59 V at 20 mA cm −2 in 1 m KOH. The CoMnB shows a comparable water-splitting current at low current range as compared with the standard benchmark electrodes of Pt/C||RuO 2 in 1 m KOH. Then, the CoMnB outperforms the benchm...

With the fast proliferation of mobile Internet, the wireless community has been increasingly looking for a framework that can provide seamless mobility. In this paper, we propose a fast cross-layer handover scheme based on movement prediction in mobile WiMAX environment. Prediction is achieved by linear regression model with keeping track of the signal strength of mobile users. With the help of the prediction, layer-3 handover activities are able to occur prior to layer-2 handover, and therefore, total handover latency can be reduced. The experiments conducted with system parameters and propagation model defined by WiMAX Forum demonstrate that the proposed method predicts the future signal level accurately and reduces the total handover latency.

Abstract-The Intermational Mobile TelecommunicationsIMT-2000 system uses a microcell concept to provide multimedia services and to support increasing number of users. However, in a microcell system, the number of handoffs is greatly increased. To solve this problem, a multitier cellular structure is proposed, in which high-speed mobile terminals (MTs) are serviced in macrocell and low-speed MTs are serviced in microcell to minimize the number of handoffs. In this system, it is important to precisely estimate the speed of the MT for the correct selection of the macrocell/microcell. We propose two macrocell/microcell selection schemes based on a new velocity estimation method in a multitier cellular system which uses the sojourn time in a microcell overlapping region. The proposed schemes have various advantages such as good performance when MT direction is varying, efficient user allocation to cells, quick velocity estimation capability, easy implementation, and low power consumption. We analyze and simulate the conventional and our proposed schemes in the Manhattan cell model, showing the proposed schemes have better performance than the conventional schemes.

Abstract-Code division multiple access (CDMA)-based radioon-fiber road-vehicle communication systems were proposed to support real-time streaming services in intelligent transportation systems (ITSs). Soft handoff should be provided for real-time streaming services because these services are required to guarantee real-time property and quality of service (QoS). However, soft handoff of real-time streaming services causes the shortage of resource in view of the system. In this paper, the doubleadjustment soft-handoff (DASH) scheme is proposed to support seamless service regardless of the shortage of resource and maximize the resource efficiency when real-time streaming services are served in CDMA-based ITSs. The DASH scheme adjusts the data rate of a call when it starts and finishes soft handoff. The performance of the DASH scheme is evaluated by analytical and simulation methods. Performances are evaluated with respect to the blocking probability, the handoff failure probability, and the carried traffic. Numerical results show that the proposed scheme can give relative good maintenance of calls and good throughput.